tof Engine 


1 Governors 


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HANDBOOKS 


— Adjustment of Engine 


Valves and Governors 


TECHNICAL PUBLISHING. CO. 
Chicago, Le 


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Copyright 1924. All rights reserved. 


TECHNICAL PUBLISHING CO. 
Chicago, III. 


Fi en 
es X05 BY 


Mee tO 18. 
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3 CONTENTS 
CHAPTER I. GENERAL PRINCIPLES OF ENGINES..... 


Use of Unaflow Principle. The Slide Valve. 
Why Valves Are Set With Lap. Development 
of the Balanced Valve. Use of Riding Cut-Off 
Valve. Corliss Valves Next Development. Re- 
leasing Mechanism of Corliss Valve. Non- 
releasing Type of Corliss Valve. Piston Be- 
comes Exhaust Valve in Unaflow Engine. Una- 
flow Auxiliary Exhaust Valves. 


CHAPTER II. DertTAIts oF MODERN ENGINES... 


Heavy Duty Frames. Cylinder Heads Used as 
Steam Jackets. Types of Cross-Heads. Four 
Types of Pistons Used. Use of Built-Up Pis- 
tons. Flywheels. How Crank Shafts Are Built. 


CHAPTER III. SETTING THE SLIDE VALVE......... 


Explanation of Lap. What Is Meant By Lead. 

Angle of Advance. Slide Valve Setting. Set- 

ting Piston Valves. Making a Piston Valve 

Templet. Setting Shaft-Governed Valves. Set- 

ting Riding Cut-Off Valves. Instructions for 
' Piston Riding Cut-Off. 


CHAPTER IV. CoRLISS VALVE SETTING.......cec- 


_ Setting Single Port Corliss Valve. Setting 
Double Port Corliss Valves. Exhaust Valve 
Setting. Adjustment of Valve Gear. Cut-Offs 
Important in Multi-Cylinder Engines. Effect 
of Change in Low-Pressure Cut-Off. Points to 
Cover in Setting Corliss Valves. 


CHAPTER V. Hour VALVE ENGINES.............; 
Setting for Lap. Exhaust Valves Should Have 
Equal Opening. Fitchburg Valve Gear. Set- 
ting Valves for Lentz Engine. Timing the 
Valves. 


58805 
ie 


5 


16 


24 


36 


44 


Cuaprer VI. .Serrrnc Ames CHUSE AND Harris- 
BURG gAMEO ow ort soe on tee ne eee + ase ee 
*® “Protection Against Loss of Vacuum  Assem- 

bly of the Ames Valve Gear. Controlled Com- 
pression. Effect of Valve Adjustments. Care 
Should Be Used in Increasing Lead. Single 
Beat Poppet Valves in Chuse Engine. Setting 
Chuse Steam Valves. How Chuse Relief Valves 
Work. Non-condensing Operation. Harris- 
burg Engine Uses Piston Valves. Setting Har- 
visburg Piston Valves. 


CHaPtTER VII. Hamitron, KinesrorD, Murray AND 
NORDBERG VALVES: .:. ). «cles «ou «ieee 


Setting Hamilton Valves. Relef Valves for 
Condensing Service. Kingsford Unaflow En- 
gine. Murray Unaflow Engines. Adjusting 
Murray Valves for Lead. Nordberg Valves 
Driven by Layshaft. Cam and Roller Clear- 
ance. Provision for Non-Condensing Opera- 
tion. . 


CHapter VIII. RipGEway, SKINNER AND~WorRTII- 
INGTON VALVE SETTING : 


Arrangement for Condensing Service. Ar- 
rangement of Ridgeway Valves. Reach Rod 
Adjustment. Skinner Unaflow Engines. 
Procedure in Setting Valves. Auxiliary Valves. 
Shifting the Eccentric. Worthington Unaflow 
Compressor. 


CHAPTER IX. GOVERNING THE ENGINE........... 


Throttling or Variable Cut-Off Used. Two 
Types of Governors. Action of Flyball Gov- 
ernor. Most Shaft Governors Use Inertia. 
Classification of Shaft Governors. 


CHAPTER I 
GENERAL PRINCIPLES OF ENGINES 


N THE development of steam engines there have been 

certain definite trends which have had to do mainly 
with the methods of getting the steam into the cylinders, 
utilizing it as efficiently as possible and then exhausting 
the steam, either to the atmosphere or to a condenser. In 
this development the simple shde valve was the first 
method of controlling the admission and the exhaust of 
the steam. Later on came the balanced types of valves 
such as the piston and then a still further development was 
the riding cut-off valve. Another important step was the 
use of Corliss valves of the releasing type and then came 
valves similar to the Corliss but of a non-releasing type. 


UsE or UNAFLOW PRINCIPLE 

All of these developments had to do mainly with get- 
ting the steam into the cylinder as no changes of any great 
consequence were involved in getting the steam out of the 
cylinder, since the same general principles were involved 
in the use of all of these types of valves, that is, the steam 
reversed itself on the exhaust stroke. ‘The engines, in 
other words, were of the counter-flow type. The next big 
development was, therefore, that of exhausting the steam 
at the center of the cylinder so that no reversal of steam 
flow was necessary. This type of engine known as the 
unaflow was the result of this further step in steam engine 
design. 

THE SLIDE VALVE 


In the earliest forms of steam engines simple slide 
valves of the D type were used. The arrangement, as orig- 
inally used was similar to that shown in Fig. 1 with the 
ends of the valves the same width as the ports so that the 
valve just covered the ports when in mid position. With 
this mechanism the center of the eccentric had to be at the 
90-deg. point on the eccentric circle so that the valve 


6 
would be in central position when the piston was at the 
beginning of the stroke as shown in Fig, 1. 


Suppose that the direction of running in this valve lay- 
out is as shown by the arrow. As soon as the shaft starts 
turning, the valve will be drawn to the right and the ports 
at the left hand or head end of the cylinder will be open 
for the entrance of steam. The port at the right hand, or 
crank end of the cylinder, begins to open for exhaust. The 
result is that the piston is forced to the right. The fur- 
ther the shaft turns, the more the valve will be moved to 


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FIG. 1. POSITION OF D VALVE WITH PISTON AT HEAD END 
OF STROKE 


the right, until the eccentric center reaches its extreme 
position at the right of the eccentric circle. Then the 
valve commences to move to the left. The force of the 
steam continues to push the piston to the right, however, 
until the valve again reaches mid position and the eccen- 
tric is directly at the bottom of the eccentric circle at 
which time the piston has reached its right hand dead 
point. 

Continuing the motion, the eccentric moves the valve 
to the left which opens the right hand end of the cylinder 
to the steam and the left hand end to the exhaust, thus 
forcing the piston to the left. The valve opens wider as 
the shaft turns, until the eccentric reaches its left hand 
position. After that, the valve begins to close until the 
mid position of the valve is reached and the piston is at 
the extreme left as in Fig. 1, and conditions are as at the 
beginning. 


7 


Wuy VALves ARE SET WitH Lap 


This arrangement will cause the engine to operate but 
it allows the steam to enter throughout the entire stroke, 
and no use is made of the work of expansion. This led to 
the use of ‘a projection on the valve called lap, which 
extended beyond the edge of the port, on the outside end 
and tended to close the ports before the piston reached 
the end of the stroke, so that the steam had a chance to 
work expansively. Since this addition delayed the admis- 
sion of steam at the beginning of the stroke, the eccentric 


FIG. 2. D VALVE ACTION WITH ECCENTRIC ADVANCED TO 
CORRECT LATE ADMISSION DUE TO LAP 


had to be turned on the shaft until the admission was 
brought back to the beginning of the stroke and this turn- 
ing ahead still further advanced the cut-off of the steam. 
The times of opening and closing the ports with the 
lengthened valve are shown after the eccentric has been set 
ahead as in Fig. 2. 

In this type of valve, the more that is added to the 
valve on the steam end, the earlier will be the cut-off. ‘The 
eccentric, therefore, has to be turned further ahead to 
bring the admission at the proper place and this again 
makes the cut-off earlier. As the cut-off is thus made 
earlier the release of the steam begins earlier, and the 
closing of the exhaust and the beginning of compression 
occur earlier. These last two effects soon become so 
extreme as to be unsatisfactory. 

When the valve has something added to it on the end 
it “laps” over the edge of the port as it stands in the 
middle position and the length that it projects over is 


8 


called the lap of the valve. The angle through which the 
eccentric is turned ahead to correct the admission after 
lap is added is called the “lap angle” and is measured 
ahead of the position the eccentric when there is no lap, 
which is 90 deg. ahead of the crank. Trial and experience 
show that the practical limit for cut-off with the D valve 
is about % stroke. 

Another defect of the simple D valve is that the pres- 
sure on the back is unbalanced and for large sizes, consid- 
erable power is used in friction between the valve and its 


FIG. 3. BALANCED VALVE WHICH OPERATES BETWEEN SEAT 
AND A PRESSURE PLATE 


seat. Another disadvantage is that the action of the valve 
in opening and closing is gradual so that free passage for 
steam is secured only after an appreciable interval. 


DEVELOPMENT OF THE BALANCED VALVE 


Several methods of balancing valves of this type have 
been used such as a pressure plate over the back of the 
valve which is carried on strips at the sides, opening being 
made through the valve, so that the same pressure acts on 
both sides. In Fig. 3 is shown a valve of this type. 

Another method has been to use a piston valve with a 
cylindrical seat in order to equalize the pressure on all 
sides of the valve. Still another form of balancing is the 
two-part valve, arranged so that one face bears on the seat 
and the other on the steam chest cover, the parts being 
separated by steam pressure to maintain their bearings. 

Quicker opening and closing were secured by the use 
of several openings at each end of the valve, or in multi- 
valved engines by a system of links to multiply the rapidity 


y 
of motion. ‘The single valve does not lend itself readily 
to such multiplying action, and extreme rapidity of open- 
ing and closing are not of so great consequence for the 
exhaust events, as for the steam events. 


UsE oF RIDING CuT-OFF VALVE 


One of the next steps which was made to overcome the 
inherent defects of the slide valve in connection with cut- 


FIG. 4. SECTION OF A MEYER REDUCING CUT-OFF VALVE 


off regulation was the development of a riding cut-off 
valve. In the simplest form, as shown in Fig. 4, this con- 
sists of a modified D valve having steam ports through the 
valve. Upon this main valve a smaller slide valve is 
operated by means of another eccentric and conirolled by 
the governor so as to cut off the steam at varying points 
of the stroke depending upon the load. The eccentric for 
this rider valve travels ahead of that for the main valve, 
so that, at the time of cut-off, the rider is travelling in a 


10 


direction opposite to that of the main valve with a result 
that cut-off is rapid and wire drawing is minimized. 
Among the advantages for this type of valve is the ease 
with which cut-off can be regulated by the governor. Being 
light in weight, little power is needed to operate the rider 
valve and the drag upon the governor in changing the 
position of the cut-off is slight so that the regulation 


x 


sees 


FIG. 5. RIDING CUT-OFF VALVE OF THE PISTON TYPE 


secured by engines equipped with riding cut-off valves is 
close. 

With this type of valve it is common to employ little 
or no steam lap on the main valve by which means it is 
possible to secure a wide range of cut-offs from 0 to 34 
stroke. 

Piston valves are built on the same princples as the 
rider valve of the D type. In Fig. 5 is shown a typical 
riding cut-off piston valve. 


CortLiss VALVES NExtT DEVELOPMENT 


One of the next important developments in steam 
engine design was the use of the Corliss type of valves. 
The essential features of a Corliss engine are: First, its 
four semi-rotary valves, two of these being for steam admis- 
sion and two for exhaust, with the latter placed at the 


11 


bottom of the cylinder to drain out condensation. Second, 
the employment of an eccentric on the main shaft, operat- 
ing the valves through radial arms in such a manner as 
to obtain rapid opening and closing of the valves. Third, 
some means of releasing the steam valve from the driving 
mechanism at the proper point in the stroke and closing 
the valve quickly by means of vacuum dash-pots. Fourth, 


FIG. 6. RELEASING TYPE OF CORLISS VALVE MECHANISM 


a governor driven from the main shaft and so arranged 
as to be entirely independent of the valve gear, its only 
purpose being to determine the point at which the release 
shall occur according to the load on the engine. 

By means of right and left hand thread connections on 
the radial arm, any valve may be adjusted independently 
of the others and the amount of lead, point of exhaust and 
the amount of compression remain the same at whatever 
point of the stroke cut-off may occur, making it possible 
to obtain nearly ideal indicator diagrams. As the steam 


12 


valves are opened quickly by means of the bell-crank con- 
nection, wire drawing is avoided. Quick closing of the 
steam valve by the suction of the dash-pots further reduces 
wire drawing and allows expansive energy of the steam to 
be fully realized in the cylinder. 


RELEASING MECHANISM OF CoRLISS VALVE 
The feature of the releasing gear, which is the most 
important part of the Corliss engine construction, is the 
hook or crab claw which engages a block on the valve-stem 


O// Supply 
Pipe.. 


.) ! Belf-crank 
' . levers---. 


cylinder-Head Cover 


FIG. 7. NON-RELEASING VALVE GEAR OF THE CORLISS TYPE 


crank arm raising the valve until the inner member of the 
hook comes in contact with the block, causing the valve 
to be released, thus cutting off the steam. Fig. 6 shows a 
typical Corliss valve mechanism. Numerous types of Cor- 
liss valves have been developed which differ from one 
another in the details of design. Some of these will be 
discussed in a later chapter, which takes up the study of 
valves of this type. 


NON-RELEASING T'YPE OF CORLISS VALVE 


In order to get away from the releasing mechanism of 
the Corliss valve and yet take advantage of this type of 


13 


valve, the non-releasing type of Corliss valve was developed 
as shown in Fig. 7. Valves of this type are usually double 
ported to reduce the amount of valve travel necessary and 
to reduce the inertia of the moving parts, in order to per- 
mit higher rotating speed and higher steam pressures for 
a given size unit, without an increase in weight of the 
engine in proportion to the power development. Some 
successful engines have been constructed with triple-ported 
valves. 


In the four-valve engine of this type, the main thought 
has been to secure a quick valve movement with as long a 
pause at each end of the travel as possible and in this way 
to secure the same result by a quick positive closing as is 
secured in the Corliss engine by releasing the valve and 
closing it by means of a dash-pot. 


Initial cylinder condensation due to the heat exchange 
between the steam and cylinder walls has always been a 
source of thermal loss within the cylinders of reciprocating 
engines. ‘This loss increased with longer time of contact, 
with greater temperature difference between the steam and 
the walls, and with the force of throw and whirl of the 
steam against the walls. 


Piston BrcoMEs EXHAUST VALVE IN UNAFLOW ENGINE 


It was a desire to reduce this source of loss to a mini- 
mum that brought about the development of the Unaflow 
engine. This engine has a cylinder with exhaust ports at 
the center which are uncovered by the piston at about 0.9 
of its outward stroke so that the valves are used only to 
admit steam. 


This type of engine was experimented with by Eaton 
in the United States in 1857 and built by Todd in England 
in 1885 but was not a commercial success until 1908, when 
Professor Johannes Stumpf, of Charlottenburg, developed 
the engine along its present lines. The features are: 1. 
Exhaust ports in the center of and around the cylinder, at 
the end of stroke, which is the means of discharging most 
of the exhaust and eliminating the counter flow of cool 
expanded wet steam. 2. An elongated piston functioning 
as exhaust valves. 3. Steam jacketed cylinder heads main- 
taining hot cylinder ends and imparting heat to the com- 


14 


pression steam. In Fig. 8 is shown a cross section of the 
cylinder of a unaflow engine. 

While the general arrangement of the valves for the 
the unaflow engine is somewhat similar to that of 
others there are certain features which require a somewhat 
different line of approach from that for the slide valve, 
piston valve, or Corliss types. Where, for instance, the 
unaflow engine is intended to operate condensing, auto- 
matic compression relief valves must be provided as a 
safety device to relieve the excessive compression pressure 


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FIag. 8. STEAM EXHAUSTS THROUGH CENTER PORTS IN 
UNAFLOW ENGINE CYLINDER 


in case the vacuum should become too low, or fail alto- 
gether. The reason that the condensing engine needs relief 
valves, is that the vacuum in the exhaust line reduces the 
steam pressure in the cylinder to such a point that, after 
the central exhaust ports are closed, the steam which is 
trapped in the cylinder cannot be compressed to more than 
75 or 80 per cent of the initial pressure. In case the 
vacuum should fail this compression pressure would exceed 
the initial pressure, hence automatic compression relief 
valves are used to reduce the compression. 


UNAFLOW AUXILIARY EXHAUST VALVES 


Where unaflow engines are designed for non-condens- 
ing operation the automatic compression relief valves are, 
as a rule, replaced by auxiliary exhaust valves located on 
the side of the cylinder at the end of the stroke. These 
exhaust valves are operated usually by the same sort of 
cam and mechanism as the steam valves, except that they 
are driven by a fixed eccentric instead of the governor. 


15 


The function of these auxiliary exhaust valves must 
not be confused with the ordinary type of exhaust valves, 
as they release only a small portion of the steam from the 
cylinder at a time when the pressure is practically zero. 
The main volume of the expanded steam is exhausted 
through the central exhaust ports, which are uncovered by 
the piston at 0.9 of its stroke, the purpose of the auxiliary 
valves being merely to delay the compression to such a 
point that the pressure in the cylinder at the end of com- 
pression stroke will be approximately 80 per cent of the 
initial pressure. 

In the design of unaflow engines generally valves of 
either the piston type or of the poppet design have been 
used. In the following chapters on the methods of setting 
valves, more details will be given of the different types of 
valves which are used with unaflow engines now on the 
market. 


CHAPTER II 
DETAILS OF MODERN ENGINES 


SIDE from the particular types of valves used on 
engines the general points of interest in engine design 
are details such as the frame, cylinder, piston, cross-head 
and connecting rod. While changes in these parts have 
not been radical, certain definite trends have been notice- 
able. 
For instance, the frame of the Corliss engine has expe- 
rienced decided changes in shape in recent years. For- 
merly the girder frame was most commonly used. ‘The 


FIG. 9. HEAVY DUTY FRAME FOR A CORLISS ENGINE 


girder frame took its name from the fact that the part of 
the frame between the main bearing and the cylinder did 
not rest on the foundation but acted as a girder supported 
by a stand or leg placed about the middle of its length. 
The cross-section of the girder frame between the guides 
and the main bearings was in the shape of the letter T to 
give greater stiffness for the weight of metal in it. The 
guides formed a part of the frame itself being either bored 
to a circular shape or planed to a V shape, hence this part 
of the frame was stiffened by the guides. 


Heavy Duty FRAMES 


Girder frames have been largely replaced by the heavy 
duty types of frame the form of which is shown in Fig. 9. 
This frame is built in one piece from the cylinder to the 
main bearing and is box shaped to allow it to rest squarely 
on the foundation throughout its length but is cut away 


17 


on the outside from the guide towards the main bearing. 
The cylinder is bolted to the end of the frame and is sup- 
ported independently. The guides are formed in the frame 
itself, and the frame is formed into a complete circle at 
both ends at the guides to give greater strength and stiff- 
ness. In some heavy duty frames the part forming the 
guides is made separate from the part containing the main 
bearing, being made in the shape of a barrel, and bolted 
to the rear section, and to the cylnider but not resting 
directly on the foundation. 


rig. 10. HEAVY DUTY FRAME FOR A UNAFLOW ENGINE 


Frames for unaflow engines have as a rule been devel- 
oped as the enclosed type and made extra heavy. In Fig. 
10 is shown a frame for a modern type of unaflow engine. 
The base of the frame extends the full length of the cast- 
ing and an oil pan is furnished under the connecting rod 
and crank, cast integrally with the frame. The bottom 
edge of the frame has a bead forming an oil-catching rim. 

It will be noted from Fig. 11 that the main bearings 
are provided with removable journals made of a bottom 
and two sides lined with babbitt metal. The bottom box 
is tongued and grooved into the frame and the quarter 
boxes are doweled to the bottom box to prevent side play. 
The quarter boxes are made extra high to eliminate the 
necessity of a top box, thereby air cooling the bearing. 

There are practically no distinctive types of cylinders, 
the principal differences being in some details of design 
and construction. Some engine makers build, cylinders 


18 


with the forward head cast solid with the cylinder but the 
general practice is to have it as an integral part of the 
frame. | 

Engines with valves placed transversely in the cylinders, 
such as Corliss engines, necessarily use cylinders of box 
section at the end. 


FIG. 11. TYPICAL ARRANGEMENT OF BEARING IN A HEAVY 
DUTY FRAME 


In unaflow engines the cylinder, is quite simple in 
design without any complication except for the central 
exhaust ports and the exhaust belt. 


CyLINDER Heaps USED AS STEAM JACKETS 


In this type of engine the cylinder heads are separate 
castings and are provided with cored passages to provide 
inlet ports and steam jackets for the inner surface. The 
jacketing insures that the inlet end is as hot and dry as 
the entering steam so that the amount of steam condensed 
is reduced to a minimum. Fig. 12 is a view of a unaflow 
engine cylinder, giving an idea as to how the cylinder 
heads are bolted to the main part of the cylinder which 
contains the exhaust ports at the center. 


19 


It can be seen that the unaflow engine cylinder is, 
therefore, in all cases separate from the main part of the 
engine frame and must be bolted to the frame and sup- 
ported by either an extension of that frame, or else by a 
separate pedestal. 


T'YPES OF CROSSHEADS 
Crossheads are of four general types: namely, locomo- 
tive, box, slipper, and H. The locomotive type is one of 
the most familiar forms of construction, for many types 


FIG. 12. CYLINDER AND CYLINDER HEAD OF A UNAFLOW 
ENGINE 


of horizontal engines using box beds. This consists of a 
hollow U-shaped casting the sides of the U being square 
in section with the crosshead end cast integral with it. 
The wearing surfaces are faced with babbitt or some anti- 
friction material and adjustments for wear are made in the 
guide. 

Box type crossheads consist of a box head casting, 
open at one end and provided with adjustable shoes at the 
top and bottom. In some constructions, the shoes are 
tapped and are adjusted by moving them forward or back- 
ward by means of bolts fastened to the crosshead cheeks. 
Another form of construction employs a wedge between 
the shoe and crosshead, adjustment being made by screw- 
ing the wedge backward or forward. 


20 


The slipper-type crosshead consists of a U-shaped cast- 
ing, attached to a slipper that travels beneath the cross- 
head guide. The crosshead pin being removable as in the 
box type. 

With H type crossheads a hollow casting with shoes 
bolted to each side is sometimes used. The lower shoe is 
made adjustable by means of screws fastened to the body 
which force the body and shoe apart or allow them to 


ose OEE 


FIG. 13. ONE TYPE OF PISTON USED ON A UNAFLOW ENGINE 


come together. In some crossheads of the box type shims 
are employed for adjustment. 


Four Types or Pistons USED 


Steam engine pistons may be divided into four general 
classes: namely, solid, hollow, conical and built-up types. 
For small engines with cylinders less than 10 inches in 
diameter the solid cast-iron or steel piston is frequently 
used, the piston rod being inserted and secured by a nut. 
Several methods are in use for securing the piston rod, one 
common construction being to have the end of the rod that 
is inserted in the piston tapered, with or without a shoul- 
der to bear against the side of the piston and secured with 
a single nut, the end being riveted over. In other forms 
the rod is made a forced fit through the piston and projects 
sufficiently to receive a nut. 

In the outside of the piston are one or more rectangular 
grooves to receive the packing rings. ‘These rings are 
turned eccentric from cast iron and cut through in one 
place in such a manner that the ends overlap. In Fig. 13 


21 


is shown a modern type of piston such as is used with a 
unaflow engine. This particular piston is of cast iron, 
with piston rings rough turned, split and ground to fit the 
cylinder bore. 

Conical pistons are used in marine work and have been 
used in some cases for stationary engines. The advantage 
of this type is its extreme rigidity for its weight. 

Built up pistons are largely used on engines of the 
horizontal type, to facilitate taking up wear which is greater 
with a heavy piston. The body is a spider with radiating 
arms to which the follower plate is bolted. A bull ring is 
placed around the spider and is supported by studs and 
adjusting nuts, and in turn supports the packing rings 
which are usually of sectional form held out by coil or flat 
springs. 


Typrs oF CoNNECTING Rops 


There are three general types of connecting rods, the 
strap, solid end and marine, each of which has its advan- 
tages for various classes of engines. The strap-end type 
consists of a rod forging of iron or steel with a forged strap 
generally attached to the rod by two bolts with lock nuts. 
The brasses are flanged on both sides and slip into the 
strap. Numerous styles of adjustment for the brasses are 
in use, one of which consists of a taper key fixed by a set 
screw. 

Liners are placed between the brasses and between the 
inner brass and the rod. As the brasses wear, liners are 
removed from between them and the wear taken up. This 
type of rod is especially adapted to engines the construc- 
tion of which does not permit of the rod being removed 
sidewise, or with a box type of crosshead in which the cross- 
head pin is part of the head itself. 

The connecting rod of the solid-end type has the end 
forged with the rod and the recess for the brasses is cut out 
by drilling holes around an outline and then finishing it on 
a shaper. The brasses are flanged on one side only, slip 
into the head, and are adjusted by wedges and bolts. 

In the marine type the rod is enlarged at the end to 
carry one-half of the box and the other half is carried by 
a separate piece which is bolted on. Adjustment for wear 


22 


is made by liners between the halves, and for length by 
liners between the inside half of the box and the rod. 

Any connecting rod may have a combination of these 
types, for example one marine end and one solid end. 

In Fig. 14 is shown a connecting rod in which the 
crosshead end of the rod is forged solid and bored to 
receive cast-iron boxes mortised and rigidly held in place 
by lock screws. It is lined with babbitt and is provided 
with wedge adjustment. At the crank end it is fitted with 
the marine type crank box. 


FIG. 14. CONNECTING ROD WITH SOLID AND MARINE ENDS 


One difficulty with the strap-end type of connecting rod 
is that it is difficult to provide a strap sufficiently heavy 
to prevent springing under over load conditions. Light 
straps are liable to cause pounding. | 


FLYWHEELS 


Flywheels are used to steady the speed against fluctua- 
tions, and to equalize the varying turning effort on the 
shaft by storing energy during the first part of the stroke, 
when the crank effort is greater than the resistance, and 
restoring it when the steam pressure decreases with expan- 
sion. On small engines flywheels are generally cast in one 
piece and forced onto the shaft by hydraulic pressure. ‘T’o 
relieve stresses moderate sized flywheels of heavy section 
are usually provided with a split hub through which heavy 
bolts pass for clamping the wheels securely to the shaft. 

For diameters too large for convenient handling or 
shipment, wheels are made in halves with bolts for the hub, 
the rim being held together by links set into recesses in 
the rim, or by bolts, or both. With this construction one- 
half of the wheel can be lowered into the wheel pit when 
erecting the engine, before the shaft is placed; then the 
upper half can be assembled on the shaft. 


23 


For large engines the weight of the wheel necessitates 
making it in sections, the sections of the rim being divided 
in a manner similar to that of the two part wheel, while 
at the hub end the spokes are bolted between two disks 
which are fastened on the shaft. 


How CRANK SHAFTS ARE BUILT 


Shafts are made in numerous forms, the principal types 
being the following: Solid forged, solid forged center 
crank and built up shafts. The solid-forged, center-crank 
shaft is forged with a projection on one side near the center 
and cut out leaving a blank for the crank which is turned 
by placing the shaft in such a position that the axis of the 
crank pin is in line with the lathe center. Such a shaft is 
generally balanced by counter weights which are bolted on. 

Built-up shafts are frequently employed in center-crank 
engines, the shaft being made in two pieces, which are 
pressed into disks and these disks connected by the crank 
pin pressed in, thus forming the crank. 

In some cases disk cranks with the pin cast solid have 
been used. A common construction is a disk crank with 
the pin pressed into it. The cranks are balanced by mak- 
ing them extra heavy on the side opposite the crank pin, 
while the plain crank is frequently balanced by weights 
bolted on, and is known as a fantail crank. 

Details described form the essential differences between 
types of engines as far as the mechanical construction is 
concerned. The main and important differences are in the 
types of valves which are used and the method of valve 
operation which is followed. For the operating engineer 
it is important that a thorough understanding of valve 
setting be obtained since the effect on the efficient utiliza- 
tion of steam due to proper valve setting is the most impor- 
tant part of engine operation. In the following chapters 
some of the details of setting valves of different types will 
be discussed in detail. 


CHAPTER III 
SETTING THE SLIDE VALVE 


HEN aslide valve is at the middle point of its travel, 

in which position the eccentric is vertically over the 
center of the engine shaft, the valve is in mid position. 
This position of the valve is used as a reference point, from 
which the parts of the valve and also its different posi- 
tions are measured. ‘The cross-section of a slide valve in 
its mid position is shown in Fig. 15. When it is in this 


V7 


a 


REE 


FIG. 15. MID POSITION OF A SLIDE VALVE 


Qa 


position, the length from the outer edge of a port to the 
outer edge of the valve is called the outside lap. This out- | 
side lap is shown by the dimensions O and O’. It is not 
necessary that the outside lap at one end of the valve be 
equal to that at the other end and in fact they are usually 
unequal, as will be explained later. The distance from the 
inside edge of a port to the inner edge of the valve is 
called the inside lap. The inside lap is shown by the por- 
tion I and I’. The inside laps of a valve are usually 
unequal, while the widths of the ports, or the distances f, 
are usually equal for both ends of the cylinder. 


EXPLANATION OF Lap 
When steam is admitted past the outer edge of the 
valve, the outside lap is usually called the steam lap and 
the inside lap is the exhaust lap. When steam is admitted 


25 


past the inside of the valve and exhausted past the outer 
edge as is sometimes done, the inside lap becomes the 
steam lap and the outside lap is called the exhaust lap. 
The steam lap is usually much greater than the exhaust 
lap, hence a valve designed for outside admission will not 
distribute the steam properly if it is used for inside admis- 
sion. Unless otherwise mentioned, the outside lap will be 
considered as the steam lap, as this is the more usual 
arrangement. 

A valve that has steam lap will keep the ports closed 
against the admission of steam until the valve moves from 


‘ 
ea [ee aes ---+-1---+- 
7 


t 
4- 


FIG. 16. VALVE SET FOR STEAM AND EXHAUST LAPS 


its mid position a distance equal to the steam lap. The 
valve shown in Fig. 16 is an outside admission valve and 
it has moved to the right of its mid position a distance 
equal to the steam lap. In this position the valve is just 
on the point of admitting steam to the head end of the 
cylinder. If the valve now moves to the right, steam will 
be admitted to the cylinder and admission will continue 
until the valve goes to the extreme right hand position 
and then moves to the left and returns to the position 
shown in Fig. 16 when the port will be closed. The port 
will then remain closed, and the steam will expand until 
the valve moves far enough to the left to bring the inner 
edge of the valve in line with the inner edge of the port. 

Further movement of the valve to the left, uncovers the 
port for exhaust, which continues until the valve, moving 
to the right on its return travel, reaches a position where 
the inner edge of the valve is again in line with the inner 
edge of the port. As the valve continues its movement to 
the right the port remains closed and the steam in the 


26 


cylinder is compressed. Compression continues until the 
valve, still moving towards the right, reaches a position in 
which the outer edge of the valve is in line with the outer 
edge of the port, when admission again occurs. It is thus 
seen that the purpose of having steam and exhaust laps is 
to permit the steam to be expanded and compressed. 

In the above action the valve is set to admit steam to 
the cylinder just at the beginning of the stroke. If a valve 
is set in this way, there will be considerable drop in steam 
pressure during admission or “wire-drawing.” 

An inspection of the diagram at the right in Fig. 
16 will show that, if the shaft rotates with a uniform 


Si 
DS aS 
Z 


FIG. 17. SLIDE VALVE SET FOR LEAD 


speed, the valve travels fastest when it reaches mid-posi- 
tion and the piston travels fastest when it reaches mid- 
stroke, the speed of each increasing during the first part 
of its motion and decreasing during the last part. This 
diagram also shows that at the beginning of the piston 
stroke the speed of the valve is decreasing as the speed of 
the piston is increasing. The result is that, if the valve is 
set to open just at the beginning of a stroke, steam cannot 
flow into the cylinder through the narrow opening fast 
enough to maintain full pressure behind the piston, hence 
the pressure in the cylinder drops. 

In order to prevent excessive pressure drop during 
admission, the valve is set so as to open slightly before the 
end of the exhaust stroke, thus insuring enough port open- 
ing to allow free admission when the piston starts forward. 
The amount which the port is opened for admission when 
the piston is at the beginning of its stroke, is called the 


27 


“lead” of the valve. The amount of lead which a valve 
should have depends upon the size of the cylinder and the 
speed of the engine, being larger for high speed and large 
cylinders and smaller for slow speed and small cylinders. 


Wuat Is MEANT By LEAD 


A valve set with lead is shown in Fig. 17, the relative 
position of the crank and eccentric being shown in the 
diagram to the right of the figure. In this illustration, 
the piston is at the head end of its stroke and the valve is 
open an amount / for the admission of steam to the head 
end, the distance / in this case is the lead. It will be 
observed that, in the position shown, the valve has moved 
to the right of its mid-position, a distance equal to the 
steam lap plus the lead. . 

In the diagram at the right of Fig. 17, the crank OC 
is shown on dead center to correspond with the position of 
the piston. The line OE shows the position of the eccen- 
tric and the distance OJ. shows the displacement of the 
valve from its mid-position. If the valve was set without 
lead, the position of the eccentric would be OH’, the distance 
OL’ being equal to the steam lap. Since the distance OL 
is equal to the steam lap plus the lead, the distance L’L 
is equal to lead of the valve. It will be observed that when 
the valve has lead, the eccentric must be turned ahead on 
the shaft from the vertical far enough to displace the valve 
from its mid-position, a distance equal to the steam lap 
plus the lead, when the crank is on center. For an outside 
admission valve connected directly to the eccentric, the 
eccentric must be set so that it leads the crank. 


ANGLE OF ADVANCE 


If the eccentric was in the position OA, Fig. 17, when 
the crank was on center, the valve would be in its mid- 
position, hence the eccentric must be moved forward 
through the angle AOE in order to displace the valve, from 
its mid-position a distance equal to the steam lap plus the 
lead. ‘This makes the angle between the crank and the 
eccentric greater than 90 deg. by the angle AOE which is 
called the angle of advance. It is the angle in excess of 
90 deg. between the crank and eccentric. The angle of 
advance is about 20 to 30 deg., but its amount will depend 


28 


upon the steam Jap and the lead which is desirable to give 
the valve. The angle of advance is important in valve 
setting as will be shown later, since it is the only thing 
about the slide valve mechanism besides the length of the 
valve rod which can be adjusted. 

Many valves, especially of the piston type, are designed 
to admit steam from the inside and exhaust past the outer 
edge of the valve. In this case the inside lap is the steam 


TABLE 1. EFFECT OF MAKING ALTERATIONS TO EXISTING 
VALVES 


By 
Increasing 
The 


Admission Exhaust Com- 


pression 


Occurs Occurs 
Outside Later earlier. 
Lap Ceases Continues 
earlier. longer 


Remains 
unchanged 


Begins as 
before 


Begins as Occurs Begins 


Remains before. later, sooner. 
unchanged. Continues Ceases Continues 
longer. earlier. longer. 


Commences Begins Commences Begins 

Angular earlier. sooner. earlier. sooner. 

Advance Period Period Period Period 
Unchanged. unchanged. unchanged. unchanged. 


lap and the outside lap is the exhaust lap. The eccentric 
follows the crank and the angle between crank and eccen- 
tric is 90 deg. less the angle of advance. 


SLIDE VALVE SETTING 


In setting the slide valve two operations are involved, 
the first of which is determining the correct position of 
the valve on its rod and the second is fastening the eccen- 
tric in position for correct angular advance. ‘To accom~ 
plish these results, the engine is first placed on its dead 
center and the eccentric temporarily fastened on the shaft, 
at approximately the place it is to be located, preferably 
ahead of its true position. Measure the lead of the valve; 
then turn the engine in the direction that it will run, 
until the other dead center is reached and again measure 
the lead. If there is any difference in the two amounts, of 
lead, the valve should be moved on the rod to equalize the 
difference. 


29 


The next operation is moving the eccentric on the shaft 
until the port is closed and then in the direction of rota- 
tion until the desired lead is obtained, finally securing the 
eccentric in position. 

It is advisable to determine the effect of making altera- 
tions to existing valves, before attempting to change them, 
therefore, table I will be of value. 


SETTING PISTON VALVES 
For the piston valve it is necessary to work by meas- 
urements, since the valve is not accessible for direct 
observation. First, make a measuring rod, as shown in 


No. 16 Gage 
Sheet Stee/: 


Wooden j Pte as ah — YY 
(Preferably Mapley< -- -F---4-- > 
Stick Rounad'-Head 
Wood! Screw 


FIG. 18. MEASURING SLIDE FOR USE WITH PISTON VALVES 


Fig. 18 for locating the steam ports in the valve chest. 
These steam port locations will, as is hereinafter described, 
be transferred to the steam port templet. The sheet steel 
head, S, may be of approximately the proportions as spe- 
cified but, in any case, the dimension L should be at least 
zg in. less than the width of the engine steam ports. Twe 
pieces of smooth clear pine, each about 1% in. thick and 
about 1 in. wide will be required. Both should, at the 
start, be about the same length as the measuring rod. All 
faces and ends should be square and true. 

Remove the valve chest cover and the valve stem stuf- 
fing box gland. Disconnect and remove the valve from the 
valve chest. Insert the measuring rod into the valve chest 
so that one of its index edges is against the further edge 
of the farthest steam port. With a knife blade, cut a cor- 
responding line, A on the face of the rod exactly at the 


30 


level of the valve chest face. Similarly, locate on the 
measuring rod lines B, C and D, which respectively cor- 
respond to the other edges of the steam ports. 


MAKING A PISTON VALVE TEMPLET 


Now, lay one of the sticks, which was prepared as above, 
on the measuring rod. With a try square and knife blade 
transfer the lines from measuring rod to the 1% in. face of 
the stick. In the illustrations, the width of the sticks is 
shown exaggerated for clearness. - Draw pencil “hatch” 
lines on those portions of the stick’s face which do not 


Steam-Port ,Port Locations. 
Termpletr Center Line} Piston Valve ,---Valve Face 
. . ‘ ’ ’ ¢ ’ s Par, <S 
2a - 


: 
aL 


Hacer ere oie 
Ran ae ae 


WA VW 


: D C . BA Pencil Hatch F ~, 
poset ING a sd Es ae: “Valve Templet™ Center Line 


FIG. 19. LAYING OUT VALVE TEMPLETS 


represent the ports. Draw, midway between CO’ and B’ a 
knife-cut center line H, across the stick’s face. This com- 
pletes the steam-port templet. 

Lay the piston valve, Fig. 19 on the 1-in. face of the 
other stick which was previously made. The left end of 
the valve should lie about 14 in. from the left end of the 
stick. Transfer to the %-in. face of the stick lines rep- 
resenting the locations of the edges of the valve faces. 
Draw a center line F, midway between the two sets of 
lines which represent the valve edges. Hatch, with pencil 
lines, the portions of the stick’s face which represent metal. 


The valve templet must be of a certain length so that, 
when in use (Fig. 20) for valve setting, it will reproduce 
accurately the events which are occuring in the steam 
chest. When in use, the lower end of the valve templet 
rests on the upper end of the valve, while the valve is 
shifted vertically to different positions. The valve templet 
slides alongside the steam-port templet. To determine the 
proper length of the valve templet proceed thus: Lay the 
steam-port templet against the valve templet (as shown 
in the right hand view of Fig. 20), with their two center 
lines F and E exactly in line. Now, the distance EH on 


£ 


31 


the steam-valve templet equals the actual distance from 
the horizontal center line between the steam ports to the 
top face of the steam chest. Also, the distance FI on the 
valye templet equals (See Figs. 19 and 20) the actual dis- 
tance between the horizontal center line of the valve and 
either end face of the valve. Hence, it follows that IJ 
is the distance which the top face of the piston valve must 


t--° Steam- 
Valve Port Templet 
Ternplet-.. 
5 4 Y Head-End 
Lines 


Representing: \g Steam Port 


Valve Eages--- >A. 
Round-Heaa 


Center Lines ¢ AP aster Fr“ 
On Templets-*,-” 4£-otrap-/ror 
fs Y Support G 
*--Crank-End ISS 
a Port 


e)<--- Va/ ve 
a chest Stud ¥\,2 


FIG. 20. VALVE TEMPLETS METHOD APPLIED TO A VERTICAL 
ENGINE 


lie below the top face of the valve chest when the valve is 
vertically central in the valve chest in relation to the ports. 
Now lay off on the valve templet below J a distance JK, 
which is equal to IJ. Cut the templet off square at K 
and it will be complete and of correct length. 

It is necessary, as indicated in Fig 20, to arrange the 
valve templet on the engine valve chest. This particular 
arrangement is for a vertical engine but a similar scheme 
may be used for horizontal engine. The main point to 
keep in mind is that the port templet must be fixed in 
some way so that it will not accidentally be moved. 

The method shown in Fig. 20 is carried out as follows: 
Bend a piece of strap iron to form a support, G, for the 


32 

steam-port templet. Drill the short leg of the support to 
accommodate one of the valve-chest studs and drill the 
long leg to take three round-head wood screws. Replace 
and reconnect the valve in the chest. Secure the steam- 
port templet to the valve chest, with the “H” end of the 
steam-port templet exactly on a horizontal line with the 
top face of the steam chest. Now place the valve templet 
alongside of the steam-port templet with the lower end, K, 
of the valve templet resting on the upper face of the valve. 
The end K should always, when the templets are in use, 
rest on the upper end of the valve. Now, if the templets 
have been accurately made, they will visibly reproduce, out- 
side of the steam chest, the invisible events which are 
occurring within it. 

To use the templets for valve setting, it is merely nec- 
essary to measure the valve events which occur from the 
templets—instead of measuring them directly from the 
actual valve and ports. In other words the procedure is 
exactly the same as for a D valve. After the valve has 
once been set correctly, it may be desirable to label and 
retain the templets for future use. But, if the proper 
trammel is made and center-punch reference marks are 
spotted on the valve stem, the use of the templet for reset- 
ting will be unnecessary. 


SETTING SHAFT-GOVERNED VALVES 


Most engines are rated about 14 cut-off, hence when 
setting a valve which is driven by a shifting eccentric, the 
governor should be blocked out to a position that will give 
that cut off. The operation is then the same as that for 
the D valve with fixed eccentric, allowing, of course, for 
the reversal of motion if a reversing rocker is used between 
eccentric and valve. After the valve is set, the engine 
should be turned over and the crosshead position noted for 
cut off at each end. Sometimes it is desirable to adjust 
for somewhat greater lead for the crank end in order to 
bring the cut off more nearly equal but the head-end lead 
should never be cut down so as to show late on the diagram 
and the lead should never be so large as to cause racing 
at light loads. 

If the governor is so made or located that it can not 
be blocked out, the setting may be made with the governor 


33 


at the innermost position as the division of lead between 
the ends is not greatly altered by the change in position of 
the governor and the exact division of lead for best action 
can be determined by the indicator diagrams. 

If the governor turns the engine around the shaft to 
alter the lead as in some of the old time motions, the valve 
is set the same as the D valve with governor in innermost 
position. 

Sertina RIDING CUT-OFF VALVES 


To set the main valve of an engine with a riding cut- 
off valve proceed as with the common D valve by equalizing 


aa Eye SSE 
ET esse — ff i A TH eM Hi 
oem aw 


tile weet 
eee eee Bata JH | 


sa = Yor LL | wien, 7 peeri Pomsiee aoe) 
YY Y 
a ; =i5 LL G \ 
—~ Sy H ) 
WSs a 
SJ 


| 2 Gi 7 
Gia , 


Ta} 


FIG. 21. SETTING MARKS FOR MEYER RIDING CUT-OFF 
VALVE 


the lead at the ends so that the valve has about 1/64 in. 
lead at each end. The main eccentric is then made fast to 
the shaft, and the setting of the cut-off proceeded with. 

Different portions of the stroke are laid out along the 
crosshead slide and from each end of the stroke. With the 
crosshead in the position at which it is desired that cut-off 
should take place, the cut-off valve is adjusted so that it 
just closes the port in the main valve, the governor being 
blocked out to running position. The engine is then 
moved to the corresponding position in the return stroke 
when the cut-off valve should just close the port in the 


34 


main valve. If the cut-off valve does not close the port in 
the main valve, the length of the valve rod should be 
changed and the cut-off is simply shifted until equal cut- 
off is obtained at both ends. 

In steam driven compressors built by the Chicago 
Pneumatic Tool Co. the Meyer cut-off valve is used on 
duplex compressors of 12-in. stroke and above. 

In this valve as shown in Fig. 21, the cut-off is adjust- 
able, allowing the compressor to operate at the most eco- 
nomical cut-off for the conditions existing. This is effected 
by means of an adjusting hand wheel which serves to 
revolve the right and left-hand-threaded valve stem thus 
drawing the cut-off valves together or spreading them 
apart. A range of from one-quarter to three-quarters cut- 
off is available and adjustment can be made while the 
machine is operating. An index block and scale indicate 
the points of cut-off. 

The valve gear consists of double eccentrics, cast inte- 
gral so that the position of the cut-off eccentric is fixed, 
once the main valve eccentric is set. 


INSTRUCTIONS FOR SETTING Piston RIDING CUTOFF 


Instructions for setting this valve are as follows: Draw 
the cut-off valves as close together as possible by turning 
the hand wheel. Set the main valve in the manner 
described for the plain D slide valve; the main valve eccen- 
tric should lead the crank by about 112 deg. 

Set the crank on head end dead center and scribe a ver- 
tical line on the crosshead and crosshead guide. ‘Then set 
the crank on crank end center scribing a vertical line on 
the crosshead guide in extension of the line on the cross- 
head. Now divide the space between the two lines on the 
crosshead guide into four equal parts scribing a line to 
indicate each division. Set the crosshead at half stroke 
and adjust the cut-off valve until it is just cutting off the 
port in the main valve. Move crosshead to the correspond- 
ing position for the other stroke, and the other cut-off 
valve should just close the port of the main valve. If it 
does not just close the port, the valve should be moved 
along on the stem to the correct position. 

These valves should be set to cut off alike at some pre- 
determined point, for the valves may be set to cut off alike 


35 


at any given position but they will not cut off exactly 
alike for any other position. 

The cut-off piston valves shown in the illustration are 
set entirely by tramming, as for a plain piston valve. On 
the main steam valve rod and the cut-off valve rod will be 
found shop tram marks with figures, indicating the dis- 
tance between them, stamped on the rod. When the valve 
rods are set so that the marks on them are apart the dis- 
tance stamped on the main valve rod, the cut-off valves 
are centered in the main valve. 

Remove the main valve from the chest and determine 
accurately the distances A, B, C, D, and HE. Replace the 
valve and connect up the valve gear. Set the main valve 
eccentric approximately 74 deg. behind the crank. Then 
with crank on head end center adjust valve stem until the 
distance from the face of the chest to exhaust ring equals 
(C+D—A). Place crank on crank end center and, using 
same reference points as before, check for distance 
(C+D+E) — (A+B). In case the distances do not 
agree, take up half of the difference on the valve stem and 
the other half by moving the eccentric. Continue in this 
manner until the lead at both ends is equal. 

The index block will be correct as it is correctly 
adjusted before leaving the factory. 

The method of setting the valve by allowing steam to 
blow through the cylinder with cut-off at various points 
should be used, and where possible the cylinders should be 
indicated. 


CHAPTER IV 
CORLISS VALVE SETTING 


HEN the various parts of a Corliss valve gear are in 
proper adjustment, the reach rod and the eccentric 
rod should be of such length that the rocker arm and the 
wrist plate will be plumb when the eccentric is vertical. 
Manufacturers of Corliss engines usually place a mark A, 
such as shown in Fig. 22, on the hub of the wrist plate 


FIG. 22. MARKING USUALLY FOUND ON WRIST PLATE OF 
CORLISS VALVE GEAR 


and three marks D, B and C on the wrist plate stud. When 
A coincides with B the wrist plate is in its central posi- 
tion and in this position the rocker arm and the eccentric 
should be vertical. When A coincides with B the wrist 
plate is at one extreme of its travel and the eccentric is on 
its dead center and when A coincides with C the wrist 
plate is at the other extreme of its travel, and the eccentric 
is on its other dead center. 

If the marks A, B, C and D are not on the wrist plate 
and stud, they should be placed on with a chisel, A and B 
being marked when the eccentric is vertical and the rocker 
arm and wrist plate are plumb, and D and C being marked 
opposite A when the eccentric is on its dead center. 


37 
SETTING SINGLE Port CoRLISS VALVE 

In order to show the method to follow in setting valves 
of the Corliss type an example will be taken of a valve of 
single port type, Fig. 23, with single eccentric. 

First, turn the engine over and see that the wrist plate 
travels equal distances each side of the central position. If 
not, make it do so by adjusting the eccentric rod when the 
gear is in one of the extreme positions as indicated by the 
marks on the hub. 

After this is done, the work of setting the valves pro- 
ceeds. The releasing mechanism for a valve of this type is 
shown in Fig. 6, Chapter I. Raise the hook rod and place 


1 ; LAP OF VALVES 
5 STEAM /EXHAUST 
LAP LAP 


% LE l 


MLL Le LL My 
T= ge) 


q (LIED addenda bidiiiddatiuu.2tn220..Qtunacnrx.rdncccQnnncccrnn ey 
WWM, 


FIG. 23. SINGLE-PORTED CORLISS VALVES 


the wrist plate in central position. Then remove the valve 
covers at the back side of the cylinder and a chisel mark 
will be found on the end of each valve. This mark is in 
line with the cutting edge of the valve and another chisel 
mark on the end of the counter bore, is in line with the 
edge of the cylinder port. With the hook on the steam arm 
engaging with the block on the dash-pot arm, the valve 
should be placed as shown in the sectional view of the 
cylinder in Fig. 23, having the steam lap and exhaust lap 
corresponding to the amount given in the table of Fig. 23 
for the size of cylinder. The rods connecting the wrist- 
plate with the valve arms have right hand threads on one 
end and left hand threads on the other so that the length 
of the connection can be made greater or less by turning 
the rod one way or the other. In this way the cutting edge 
of each valve can be placed in the proper relation to the 
corresponding port edge of the cylinder as given by the 
table. 


38 

When valves are set the engine crank should be placed 
on one of the dead centers, say the one nearest the cylinder. 
The piston is then at the end of the stroke towards the 
head end of the cylinder. Move the wrist plate until the 
hook rod drops into place on the driving pin. Then 
examine the steam valve on the head end of the cylinder. 
The mark on the valve should be 344 in. nearer the center 
of the cylinder than the line on the cylinder corresponding 
to the edge of the port, this 4g in. opening being called 
steam lead. If it is much more or less than + in., loosen 


ra 
= 
wl 
= 
@ 
o 
w 
2 


Hi 


My VE MM 
Yj 


WT ace ibgudisddbbissideda 


Wh 


FIG. 24. DOUBLE-PORTED CORLISS VALVE 


the set screws in the eccentric and move the eccentric on 
the shaft one way or the other until the valve is in the 
correct lead position. When the correct position of the 
eccentric is found, mark the eccentric and shaft to cor- 
respond in such a way that it can be detected later, should 
the eccentric slip from its correct position. Then fix the 
eccentric on the shaft and replace the back valve covers 
and the engine should be ready to operate. 


SETTING DOUBLE-PorRT CoRLISS VALVES 


For setting valves of Corliss engines with double eccen- 
trics and double-ported valves as shown in Fig. 24, the 
Bates Machine Co. gives the following instructions: 

On the hub of the wrist plate, or of the steam valve 
crank where no steam wrist plate is used, and on the wrist- 


39 


plate base, or steam bonnet, will be found the chisel marks 
referred to at the beginning of the chapter. 

If the back valve-covers of the cylinder be removed, 
chisel marks will be found on the ends of the valves, and 
on the ends of the valve chamber counter bores, as for the 
single ported engine. 

Steam valves are set by the same process as for the 
single-ported, single eccentric engine, but given a negative 
lap, about 3%; in. for a cylinder 18 in. diameter and steam 
lead about 34¢ in. 


EXHAUST VALVE SETTING 


To set the exhaust valves, proceed in the same manner 
by raising the hook rod and placing the wrist plate, (for 
double eccentric engines, use the exhaust wrist plate), in 
the central position. The valve edge and port edge of each 
exhaust valve should then be brought in line with each 
other by adjustment of the valve rod connecting the wrist 
plate and exhaust arm, giving the valves zero lap in the 
central position. This is the only adjustment for a single 
eccentric engine. | 

For a double eccentric engine, now turn the engine over 
until the cross head is about 4 in. from the end of the 
stroke, say towards the head end. The exhaust eccentric 
should then be moved on the shaft, until the exhaust valve 
at the head end of the cylinder has its cutting edge in line 
with the port edge of the cylinder. This will give the 
proper compression for a medium sized cylinder, 22 to 24 
in. diameter. For a smaller cylinder it will be better to 
place the cross head about 314 in. from the end of the 
stroke and for a larger cylinder about 41% in. 

Tighten the set screws in the eccentric, also nuts which 
have been loosened in making adjustments; replace the 
back valve-covers and then the engine should be ready for 
operation. 

Steam valves on engines with double eccentrics are 
given negative lap in order to give a later cut-off- where 
the load demands it. Where negative lap is used, it is 
necessary that the governor knock-off cams should be placed 
so that the dash-pot closes the valve at every stroke, other- 
wise there would be live steam on both sides of the piston 
at one point in every stroke. 


40 


ADJUSTMENT OF VALVE GEAR 


During the course of the valve setting work, it is well 
to note the clearance around the catch block. It is impor- 
tant to adjust the length of the dash-pot rods properly, 
because, if they are made too short, the valves will not hook 
on and, if they are too long, the valve stem is liable to be 
bent or the steam brackets broken or both. 


Yoke Fin. Spindle top: 
Steam Hook Spring. Hele for loadirg with shyt ran Fendulum Arm Yokes. 
Gov Rod Brass Heads. RS) 
Ys 


Doble Ary Connetling Arm Ling 


Hole for Wace sot \ CY Vs 
team Brackets. Center Weight Bell Bearing 


ie) 
Link Cellar Fin. Wr. Ba//. 
Link Co/lar. Ne, 


dle Sleeve 9 
“i sehode- ted $f «— Orep Red Brass Head 


DY \) Va S Cress Bar. . 
tS Long Gov Fred Cov Dash Por Bressth I Ay 
Knock Off Lever. Gov. fe (Es ie - a Spindle Bal! Beering. 


w a Center Weight 
YN Pandilun Arm. 
Connecting Arm 


ofety Cam. Gor Dash Fe 4; (ae) 
Vetth Plate \ pceal\ ita! p55 ig ful Ss yoindle. 
Staem Hoek. al \ Che Gres3 Head Re Governor Orep Pod 
7 aN Kw nm Drop Rod Arrn. 
Be// Crank Shof »\ ct Pp 
Safely Comes Ps) Ball Crank 0 “) \ 
Knock Off Cam Govarror Calica 
i a 
Short Gov Kod. be) 
Bell Crank Boering Collar: Spindle. 
Gov Dash For Cover: 
Gov. Dash Fort — Bobositt 


Dash Pet Plunger: 
Adjusting Plate 
a bbsTr. 


Smee! Gor Fulley. 


XS YK es: gs 


FIG. 25. METHOD OF HOOKING UP A GOVERNOR WITH 
CORLISS VALVE GEAR 


4 Stand Suppor’. 


Mitre Gears. 


The governor and governor rods should next be ad- 
justed if they require it. Figure 25 shows a common form 
of Corliss engine governor with its connection to the valves, 
parts of the governor being cut away to show its construc- 
tion. As shown here the parts of the governor are in the 
position they will occupy when the engine is running at. 
normal speed. If the speed rises about normal, centrifugal 
force throws the govérnor balls farther from the center. 
This raises the cross bar, carrying with it the drop rod 
arm, and throws the knock-off lever on the valve stem so 
that the knock-off cams strike the steam hooks earlier thus 
causing an earlier cut-off. If the speed falls below normal, 
the knock-off cams are moved in the opposite direction and 
cut-off occurs later. 


4] 


If the belt which drives the governor should break, the 
cross bar would drop to its lowest position and this would 
make cut-off come at the latest possible point in the stroke, 
or the steam hooks would not be disengaged at all so that 
the cylinder would take steam for the entire stroke, which 
would cause the engine to run away. 

In order to prevent that possibility, safety cams are put 
on the knock-off lever. When the governor falls to its 
lowest position, the governor knock-off levers are thrown 
around far enough to bring the safety cams under the 
steam hooks thus preventing the admission of any steam to 
the cylinder. If the safety cams are allowed to come into 
action as described above, the engine cannot be started 
after it is shut down until the governor is raised high 
enough to prevent the safety cams from coming in contact 
with the hooks. It would be a nuisance to have to raise the 
governor every time the engine is started so a safety device 
is placed on.the governor to prevent it from falling to its 
lowest position and bringing the safety cams into action 
when the engine is shut down by hand. 


Cut-orrs IMPORTANT IN MULTI-CYLINDER ENGINES 


Setting the valves on a compound or triple expansion 
engine of the Corliss type is precisely the same as for a 
single engine except that the adjustment of cut-offs in the 
various cylinders is largely a matter of “cut and try” until 
best results are obtained. This is usually considered to be 
at points where an equal load is carried by each of the cyl- 
inders. 

An increase of cut-off in the high pressure cylinder, 
while the initial steam pressure and the cut-offs of the 
intermediate and low-pressure cylinders remain as before, 
results in an increase of the pressure in the first and second 
receivers an increase in effective pressure in all three cyl- 
inders and consequently results in an increase in horse- 
power of the engine. Conversely an early high-pressure 
cut-off without change of the other cut-offs and initial 
steam pressure causes a decrease in receiver pressures, 
effective pressures and horsepower. 

Lowering the initial steam pressure in the high-pressure 
cylinder without change in cut-off results in lower receiver 
pressures, lower effective pressures and lower horsepower. 


42 


Conversely, if, under the same conditions, the initial steam 
pressure is raised, the receiver pressures, the mean effective 
pressures and the horsepower will be increased. 

Other conditions remaining the same, if the interme- 
diate cylinder cut-off is made later, the pressure in the 
receiver and the intermediate cylinder is less and the drop 
from the high-pressure cylinder increases, whereby the 
power developed in the high-pressure cylinder, owing to the 
increase in the effective pressure, 1s increased. At the same 
time the mean effective pressures in the intermediate and 
low-pressure cylinders decrease, hence the horsepower there 
developed will be decreased. The converse of this is also 
true. } 


EFFECT OF CHANGE IN LOW PRESSURE CUT-OFF 


Again, suppose that other conditions remaining the 
same the low-pressure cut-off is made later; then the pres- 
sure in the second receiver will be lower the mean effective 
pressure in the low-pressure cylinder, hence the horse- 
power there developed, will decrease. At the same time, 
the mean effective pressure in the intermediate cylinder 
increases, hence the horsepower there developed will in- 
crease but no change will take place in the high-pressure 
cylinder. 

If, under the same conditions, the low-pressure cut-off 
is made earlier, the horsepower developed in the low-pres- 
sure cylinder will be increased, that of the intermediate 
cylinder will be decreased and that of the high-pressure 
eylinder will remain unchanged. 


PoINTs TO REMEMBER IN SETTING CORLISS VALVES 


In general the setting of Corliss valves may be sum- 
marized as follows: 

1. Remove the steam and exhaust bonnets and upon 
the end of each valve will be found a mark corresponding 
to the opening edge of the port. The direction for opening 
the valve can be determined by working the wrist plate by 
hand. 

2. Examine the wrist plate hub and bracket. Upon 
the bracket will be found a mark corresponding to the 
central position of the wrist plate and two other marks 
locating the extreme travel of the wrist plate in either 
direction of motion. 


43 


3. See that the rocker arm travels equal distances 
each side of the vertical position. ‘To do this loosen the 
eccentric and rotate it slowly about the shaft. Then with 
a plumb bob and scale, measure the distance the rocker 
arm travels each side of its central position, and adjust the 
eccentric rod, to bring the distances equal. 


4. Rotate the eccentric about the shaft and see that 
the wrist-plate travels equal distances each side of its 
central position as shown by the travel marks. If it does 
not, adjust the length of the reach rod to bring them equal. 


5. Block the wrist-plate in its central position, then 
pull up the dash-pot rods until the hook pins engage with 
the steam hooks. Adjust the length of the steam and 
exhaust radius rods until the valves have the proper amount 
of lap as determined by size and speed of engine table. 


6. Throw the wrist plate with the starting bar, first to 
one, then to the other extreme position and adjust care- 
fully the length of the dash-pot rods so that the steam 
hooks will latch with the hook pins when the wrist plate is 
at its extreme travel, allowing 35 in. for clearance. 


v7. Place the engine on dead center and see that the 
reach rod is fastened to the wrist-plate. The eccentric 
should then be turned in the direction that the engine is 
to run until the proper amount of lead is secured and the 
eccentric is then fastened to the shaft. Place the engine on 
the opposite dead center and measure the lead. If it is 
not the same, make it the same by adjusting the length of 
the steam radius rods. 


8. Block the governor up half way in the slot and 
fasten the reach rod lever at right angles to a line drawn 
half way between the two rods. Adjust the length of the 
reach rods until the knock-off arms stand vertical; with 
governor in this position, turn the engine over until cut- 
off occurs and measure carefully the distance the crosshead 
has traveled ; place the engine so that the crosshead will be 
the same distance on the other stroke and adjust the length 
of the reach rod until the cut-off will just occur. 

9. Drop the governor to its lowest position and see 
that the safety blocks on the knock-off cams are adjusted 
so as to prevent the steam hooks from latching with the 
hook pins. 


CHAPTER V 
FOUR-VALVE ENGINES 


S MENTIONED in the first chapter, the four-valve 
principle has been applied to engines using different 
types of valves. One development of the four-valve type 
has been the building of a valve gear similar to the Corliss 


“Frame Reach Sa 
: Roa, Steam Eccentric 
Rod. 


vFrame Reach 
i Rod, Exhaust 


Cylinder Reach Roa. Steam 


Wrist 
Plate:, 
vExhaustArm + of 


Rocker Arm-- 
Front Exhaust 


I El a 
Beg 


Rocker- ‘+ Exhaust Eccentric Rod 
a se, él Arm 

“Exhaust-Valve Link Rod's? Bracket“ 
Il- Elevation 


FIG. 26. NON-RELEASING TYPE OF CORLISS VALVE GEAR 
USED WITH BALL ENGINE 


tvpe but different in that no releasing mechanism ‘is used. 
Engines of the four-valve type have also been fitted with 
grid-iron valves and with poppet valves. 

One engine of the non-releasing Corliss type is the Ball, 
the valve gear of which is shown in Fig. 26. In setting 
the valves for this engine, the eccentric rod is adjusted so 
that the rocker arm travels equal distances on each side of 
the vertical position. The eccentric is then blocked up with 
the governor weight arm in its extreme outer position. In 
this position the center of the eccentric is in line with the 
centers of the suspension pin and of the shaft. Next the 


45 


engine is turned over until the steam valve at the crank 
end, moves as far towards opening as it will. If the valve 
does not come within s'; to 7g in. of uncovering the port, 
the reach rod connecting the rocker arm to the steam arm 
should be adjusted until the valve is in the position 
stated. 


SETTING FOR LAP 


When the engine is turned over until the head-end 
valve is moved towards its open position, the lap at the end 
of the valve travel should be 74 to 35 in. If it is not, the 
cylinder reach rod which connects the two steam arms 
should be adjusted. If this is done, the engine will not 
take steam when the speed throws the governor weight to 
its extreme position. An indicator is necessary to adjust 
the point of cut-off accurately for the two ends. The cut- 
off should be adjusted with the indicator so that it is prac- 
tically the same at both ends. As there is considerable 
wire drawing at no load, this should not be eliminated. 
The pressure before cut-off should be about half the pres- 
sure at the throttle. 

In setting the exhaust valve, the link connecting the 
two exhaust valve arms should be equal in length to the 
distance between the valve centers, for cylinder diameter of 
less than 19 in. Where the cylinder is more than 19 in. 
an exhaust wrist-plate is used and the exhaust valve link 
should be adjusted so that, when the wrist-plate is turned 
to bring the wrist-plate pin and the two link pins in a 
straight line, the exhaust valves should cover the ports 
with equal lap on both edges of the ports. 


EXHAUST VALVES SHOULD Have EQuaL OPENING 


When the engine is turned over, the two exhaust valves 
should open equally. If not, adjust the length of the valve 
rod until both port openings are equal. ‘The exhaust eccen- 
tric on the shaft is now moved so as to cause compression 
to begin at the desired point. This should be such that 
the compression pressure will rise to about half the throttle 
pressure. Head-end compression should be a little greater 
than crank-end. ‘The correct amount is the least compres- 
sion with which the engine will run smoothly. 


46 
FITCHBURG VALVE GEAR 


To set the valves of the Fitchburg engine (Fig. 27), 
first adjust all rods and connections so that the several 
parts will travel equally on both sides of the center in a 
complete revolution of the engine. As the engine has two 
eccentrics, one for the steam valve and one for the exhaust 
valve they should be set separately. Ignoring for the pres- 
ent the exhaust valves, place the latch of the steam valves in 
the center of the spiral block and clamp the hook by its 
lever, adjusting the movement of the wrist cranks by the 


=e = 
Uy) Pe Ve cS 
eg 

lil 


FIG. 27. FITCHBURG VALVE GEAR 


right and left connection as provided. Set the engine 
exactly on the dead center and move the small rod attached 
to the head valve in or out of its cam until the port is 
opened the proper lead, which is usually about 3g in. and 
tighten the set screws in the neck of the rod. Roll the 
engine on the other center and proceed as before. 

To set the exhaust valve, adjust for equal travel as 
usual and set the eccentric on the shaft so that the exhaust 
valve for each end will close the port when the piston is 
about 1 of the stroke from the end. It is best to spot all 
set screws to prevent slipping. 


SETTING VALVES FoR LENTZ HNGINE 


In the Erie City Lentz Engine the valves used are of 
the poppet type driven by eccentrics mounted on a lay 
shaft. These valves are of the double-seated balanced type. 

In Fig. 28 is shown the arrangement of the valve gear 
for this type of engine. An admission valve eccentric is 
used which has an oblong slot in it to permit side travel so 
that the action of the governor will change the point of 
cutoff. The exhaust valve eccentrics are fixed in definite 


47 
position but may be advanced or retarded to control the 
point of release and the amount of compression. 


In order to set the steam valve, the lay shaft is turned 
until the eccentric rod of the valve is at right angles with 


FIG. 28. VALVE GEAR OF ERIE CITY LENTZ ENGINE 


the driving block which is linked to the governor. If the 
governor is now opened and closed from maximum to 
minimum positions, the steam cam lever should show but 
a slight movement. This position of the eccentric is the 
one which it assumes when the steam valve is to open and 


48 


ANIONDT ZLNAT NI LAVHS AVI V AG NHAINA AUV SHATVA LaddOd 


LQG * 
— 


SSS 


12) 2 
; =, ),, myn Ye 
2) PU” ae MME 


LM 


“6% ‘DId 


49 


the valve stem or spindle should be adjusted by screwing 
in or out of its upper end so that the roller just touches 
the cam, and so that the movement of the eccentric raises 
the valve. This is the position of the valve with the engine 
on dead center. 


TIMING THE VALVES 

Timing of the entire valve gear is accomplished by 
shifting the bevel gear driving the lay shaft, one or more 
teeth. On the latest type engine, however, this is more 
conveniently accomplished by removing the bolts in the 
coupling flange on the lay shaft, located between the gov- 
ernor section and the gear section and moving the gover- 
nor section the desired distance and in the desired direc- 
tion, then inserting the bolts in the flange in the new 
position. ° 

Shifting the steam eccentric ahead causes the lead to 
be greater and cutoff earlier. Shortening the eccentric rod 
will likewise increase the lead and give a later cutoff. The 
adjustment of the exhaust valve is made by shifting the 
eccentric ahead to get earlier release and compression. 
Shortening the rod will give earlier release and later com- 
pression. 

‘These valves are tram marked at the factory with a 
punch mark on the valve stem and on the roller guide or 
crosshead. ‘These marks are 2 in. apart. In case of 
removal and replacement of the valve, the stem length may 
be made as originally set by tramming this distance. 


CHAPTER VI 


SETTING AMES, CHUSE AND HARRISBURG 
VALVES 


N THE Ames unaflow engine, steam is admitted to the 
cylinder by a double beat poppet valve which is lifted 
by a roller in a square section sliding bar, when it comes in 
contact with the lifting cam. This cam is carried in a 


FIG. 30. SECTION THROUGH BONNET AND VALVE OF AMES 
ENGINE 


cylindrical bronze cross head attached to the valve stem 
and the valve is closed by the coil spring on the top of this 
crosshead, the top of the spring bearing against the bonnet 
eap. In Fig. 30 is shown a section through the bonnet and 
valve which is used for steam admission. ‘The exhaust as 
with all unaflow engines is through a center belt of ports. 


51 


When the engine is built for non-condensing service 
the piston has concave heads. ‘This provides enough clear- 
ance volume to reduce the compression pressure to a reason- 
able amount. 


PROTECTION AGAINST Loss oF VACUUM 


For condensing operation the piston has straight ends 
and the clearance is made as small as possible. In order 
to protect the engine, if the vacuum should be lost, an 
automatic by-pass valve is used such as is shown in Fig. 31. 


FIG. 31. BY-PASS VALVE PROTECTS THE ENGINE AGAINST 
HIGH COMPRESSION 


These valves are controlled by the condition existing in 
the exhaust belt of the engine. They operate only with 
loss or restoration of vacuum and do not operate with each 
stroke of the engine. The small pipe is connected with the 
exhaust belt or exhaust pipe of the engine, thus com- 
municating the conditions in the exhaust belt to the syl- 
phon which is attached to the valve stem. 

- By the action of the vacuum the sylphon is collapsed, 
the coil spring compressed and the valve held firmly to the 
seat, which reduces the clearance in order to secure proper 


52 


compression for condensing service. If the vacuum is par- 
tially or totally lost the spring will open the valve which 
connects a clearance pocket in the cylinder head with the 
clearance in the cylinder thus increasing the total clear- 
ance volume and preventing undue compression during 
non-condensing operation. When the vacuum is again 
restored, the valve closes as above described. 

It is possible to change the tension of the spring by 
adjusting screws, so that the point at which the valve opens 
and closes can be varied to a reasonable extent. 


ASSEMBLY OF THE AMES VALVE GEAR 


Assembly of the valve gear is made on the basis of 
tram marks on the rods and rod heads which have been 
marked at the factory. These marks are stamped upon the 
rods after the valves have been set and before the engine 
is dismantled on the testing floor. If the engine, for any 
reason, has not been tested before shipment, the rods will 
not be marked, in which case the eccentric rod should first 
be connected to the rocker lever and so adjusted that the 
rocker lever over the frame travels equal distances either 
side of the vertical center line. 

First adjust the valve stem so that there will be about 
0.002 in. space between the flat part of the cams and the 
roller in the roller rods. ‘This space is conveniently meas- 
ured by using a thickness gage through the peep hole open- 
ing in the side of the bonnet. This space of 0.002 in. will 
be slightly increased as the valve stem expands when sub- 
jected to the steam temperature and should be about 0.003 
in. when the engine is in operation. 

With the valve stems adjusted as above, place the rod 
over the frame in position as shown in Fig. 32, turn the 
engine to its crank end dead center and adjust this reach 
rod so that the roller in the crank end roller rod just 
touches the cam. Then with the engine on its head end 
dead center, adjust the ball rod over the center so that the 
roller in the head and roller rod will just touch the cam or 
about the same as the crank end. 

This is in the nature of a preliminary setting, only, 
and further adjustments will be necessary after the engine 
is In operation. In the illustration previously referred to, 
the controlled compression type of engine is shown. This 


53 


type of engine is used where it is desired to exhaust against 
back pressure of from 2 to 15 lb., where steam is required 
for low-pressure heating, drying or other purposes. 


CONTROLLED COMPRESSION 


In this case, secondary exhaust ports and valves are 
located directly at the ends of the cylinder so that the final 
exhaust closure is not controlled by the piston covering the 


eo — 


FIG. 32. CONTROLLED COMPRESSION IS OBTAINED BY 
ADJUSTMENT OF EXHAUST VALVE SETTING 


secondary exhaust ports. This construction permits of the 
compression being controlled at will, as it is possible to 
vary the time of the final exhaust closure to such an extent 
that any desired compression pressure may be obtained 
under widely varying admission. 

In setting the exhaust valves remove the covers on the 
opposite side of the cage from the rocker lever, which will 
allow a full view of the side of the cams, then turn the 
engine over in the direction of rotation until it is on its 
dead center, and make a mark on the side of the cross- 
head shoe and a similar mark on the crosshead guide 
directly in line with the one on the crosshead shoe. Turn 


54 


the engine to the other dead center and mark it in the 
same way. ‘This will provide for conveniently measuring 
the distance the piston may be from the end of the stroke. 

Turn the engine over until the piston is within 1 in. 
of the head end dead center from the expansion stroke and 
adjust the reach rod D shown in Fig. 32 so that the cam 
in the crank end cage’is just in contact with the roller. 
Turn the engine over until the valve is seated and measure 
the distance the piston is from the crank end. This will 
determine the length of the compression which should be 
approximately 20 per cent of the stroke in ordinary cases, 
and in any event will be close enough for preliminary set- 
ting. Turn the engine to the crank end dead center and 
adjust the valve rod E to open the head end valve in the 
same manner as the crank end valve. 

With the valves thus set, the engine may be operated 
and the rods further adjusted to gain the best results by 
using the indicator after the engine is in operation. ‘The 
roller in the small crosshead on the exhaust valve stem 
should be adjusted through the small rectangular opening 
on the side of the cage so that there will be about 0.003 in. 
space between the cam and roller at a point on the round 
part of the cam just before the lifting part comes into 
contact with the roller. 


EFFECT OF VALVE ADJUSTMENTS 


In Table II the effects of adjustments made on the 
exhaust rods and change in location of the exhaust eccen- 
tric on the shaft are shown. The exhaust valve gear is 
fully as sensitive to adjustment as the admission valve gear 
and only slight adjustment will have a pronounced effect 
on the indicator diagram. 

In order to set the valves more accurately, it is neces- 
sary to take indicator diagrams after the engine has been 
operated for a short time and is warmed up. Any adjust- 
ments to the valve gear necessary to change the valve set- 
ting should be made with a view of properly adjusting the 
crank end valve first, giving no attention whatever to the 
head end valve until the crank end valve has been satisfac- 
torily adjusted, bearing in mind that the valve motion is 
sensitive to adjustment and little change on rods is re- 
quired to make a material change in the indicator diagram. 


55 


With the crank end valve satisfactorily adjusted, the 
head end valve should be adjusted in the same way. It 
should be understood that, due to the angularity of the 
connecting rod and eccentric rod, it is not possible to 
obtain as good a diagram from the head end as from the 


TABLE II. CHANGES IN EVENTS DUE TO VALVE ADJUSTMENTS 


Adjustment of Steam Valves. 


ee 
Adjustment - 
feat [Atniosion | toot | 


Shortening reach rod A Later Lighter Earlier Heavier 
Lengthening reach rod A Earlier Heavier Later Lighter 
Shortening ball rods B Unchanged Lighter Earlier Heavier 
Lengthening ball rods B Unchanged | Heavier Later Lighter 


Adjustment of Exhaust Valves 
(Engines up to and including 30 inch stroke) 


Crank End | Head End 


in SA a es Valve 


Shortening reach rod D Earlier Later Later Earlier 
Lengthening reach rod D Later Earlier Earlier Later 
Shortening valve rod E Unchanged Unchanged Later Earlier 
Lengthening valve rod E Unchanged | Unchanged Earlier | Later 
Moving exhaust eccentric around 

the shaft in direction of 

TOTATLONecccccccccccccoee | Later Later Earlier Earlier 
Moving exhaust eccentric 

around the shaft in opp- 

osite direction of rotat- 

LOiNe ese lale'w ale.ele o.6's o ele e 60-6 0 Earlier 


Adjustment 


‘Adjustment of Sxhaust valves 
(Engines 34 = inch to 36 - inch stroke) 


Crank ind | Head End 


Adjustment 
Valve pei votre ase 


Opens Closes | Closes 


Shortening reach rod D Later Larlier Later 
Lengthening reach rod D Zarlier Later Earlier 
Shortening valve rod 3 Unchanged Unchanged Later 
Lengthening valve rod E Unchanged| Unchanged farlier 
Moving exhaust eccentrics 

around the shaft in dir- 

ection of rotation....... | Zgrlier Earlier Later 
Moving exhaust eccentric G 

around the shaft in opp- 

osite direction of rota- 

ELON cecccccvcccccscsecce Earlier | Earlier 


crank end with a shaft-governed engine of any type. In 
most cases the lead will show later and the admission line 
will not be as good as for the crank end and, if there is 
any difference in compression, it will show higher on the 
head end. 

Various indicator diagrams are shown in Fig. 33 which 
will give a general idea of the type of diagrams from one 
of these engines. 


56 
CARE SHOULD BE USEp IN INCREASING LEAD 


Care should be exercised when increasing the lead on 
the valves with the engine carrying a load, that the lead is 
not increased so much that the governor will lose control 
of the speed when the engine is operating at friction load. 
This is quite possible, as the rollers may be adjusted so far 
under the cams with the engine carrying a load, that when 
the load is thrown off and the governor is on its minimum 


fads calor Diagrams F2°Or77 /77a'Cato eagraiis Fro 
UiaFlow Lr7gire. Controlled—-Cormi pvessior 


Unae-F/OowWw 
Ail Diagrams Taken 


ie Non Condensing 


Diagram Shows Lead, Late O17 The 
Head End. 


Non-Corden sing 


Diagram Shows Lead, Late On The 
Head End. 


Won-Condensisig 
Head 


Ya Nae ae 


Diagram Shows Lead, Late O17 THe 
Crank End 


ee 


Diagram Shows Lead, Late OnThe 
Cranh Erd 


07. Condensing ee 


Diagram Shows Crank Ead Exhaust 
Valve Closes Too EFerly Cawsii7 
wigh Compression On Crank End 


Correct Non- Condensing 
Diagram 


Diagram Shows Head End Exhaust 
Valve C1ESCS Joo Early Couvs/7g 
nigh Compression On Head End. 


Condens 171g 


Correct Condensing Diagram f Correct Diagram 


FIG 33. EFFECT OF VALVE SETTING ON INDICATOR 
DIAGRAMS 


57 


travel, the roller may still be coming in contact with the 
cams and lifting the valve slightly, admitting steam into 
the cylinder, causing the governor to lose control of the 
engine. 

In this case it 1s necessary to decrease the lead only to 
such an extent that the governor will control the engine at 
the friction load which is a maximum lead and should be 
given to the valve with maximum steam pressure. 

If the engine is to operate sometimes condensiyg and 
at other times non-condensing, the valves should be set for 


Rolle Sa A 
i 


eS is 
Roller slide — 4 ll E Cam 
Eko A 
aes nee Sp ere te Od Aes 


< Reach rod == Crosshead 


Balland socket 


_——— 
Sal CAE a —m 
iene 7 coe 
yee aus HCl 
YL Yes ii Yh ee f Sea sos . 


FIG. 34. CAM HEAD AND VALVE OPERATING MECHANISM OF 
CHUSE ENGINE 


the condensing operation as a condensing engine will not 
operate satisfactorily with as much lead when operating 
condensing as it will non-condensing, due to the action of 
the vacuum in addition to the early admission of steam. 


SINGLE-BEAT PoPpPpET VALVES IN CHUSE ENGINE 


In the unaflow engine built by the Chuse Engine & 
Manufacturing Co., admission valves are of the single-beat 
poppet type. It will be noted from the sectional view of 
this valve shown in Fig. 34 that the valve assembly con- 


58 


sists of a camhead, roller-slide, the valve and valve stem. 
The roller slide is operated by the rocker arm driven by the 
governor eccentric. ‘The roller slides under the cam and 
lifts the small crosshead that carries the valve stem and 
valve. 

In this construction, the valve stem is slipped through 
the center of the valve and is held in place by a screwed 
jam-nut. The upper end of the stem screws into a cross- 
head, which slides.in the valve bonnet and carries a cam. 
A roller is carried on the roller slide which reciprocates in 
the housing and the roller by lifting the cam opens the 
valve. 

The slide rod is fastened to the reach rod by a ball 
and socket joint and the reach rod in turn is fastened to 
the steam rocker arm. This arm is of the indirect type 
causing the reach rod to move to the right when the eccen- 
tric rod and eccentric move to the left. 


SETTING CHUSE STEAM VALVES 


To set the steam valve it is first necessary to locate the 
crank in center position and the reach rod is next uncou- 
pled and the rocker arm adjusted so that it travels equal 
distances from its vertical position. By uncouphng the 
ball and socket joint it is possible to disconnect the reach 
rod from the lower slide rod and the top half of the valve 
may then be removed. ‘This exposes the slide rod and cam 
of the valve stem crosshead. The slide rod should then be 
shifted to.bring the roller under the high or thin part of 
the cam. The clearance between the roller and cam should — 
be approximately 0.004 in. This clearance should be care- . 
fully checked by slipping a feeler gage between the roller 
and cam and the valve stem should be screwed in or out 
of the crosshead to bring this clearance to the value given, | 
if it is not correct. If the clearance is too small when the 
engine warms up, expansion may cause the valve to remain 
open at all times. 

After adjusting both head and crank end valves the 
bonnet should be replaced. The next step is to connect up 
the reach rod and place the engine on crank-end dead cen- 
ter. After this is done, the reach rod should be lengthened 
or shortened to give the valve a lift of 35 in. with the 
engine on dead center. To measure this lift a punch mark 


> 59 


should be placed on the upper edge of the valve stem 
housing, at the part marked O in Fig. 34 and a second one 
on the valve stem locknut. This should be measured with 
the valve closed and when the engine is on dead center. 

After this is done the engine should be turned to the 
head end dead center and the rod A adjusted until the 
head end valve has the same lift or lead. 

Where the engine is intended to operate condensing, 
automatic compression relief valves are provided as a 


FIG. 35. AUTOMATIC COMPRESSION RELIEF VALVE 


safety device to relieve the excessive compression in case 
the vacuum should become too low or fail all together. One 
of the automatic relief valves is shown in Fig. 35. 


How CHusE RELIEF VALVES WoRK 


Considering the valve A closed for condensing opera- 
tion as shown, live steam is admitted through pipe D to 
chamber B. The excess pressure which holds the valve A 
closed is due to the greater area of the valve body in cham- 
ber B compared to the area of the port leading from the 
cylinder. ‘This difference in pressure is sufficient to hold 
the valve A closed under ordinary initial pressure in the 
cylinder. | 


60 


If the compression becomes excessive, due to the failure 
of the vacuum, the valve A is forced off its seat, opening 
the small valve C and throwing the chamber B into com- 
munication with the atmosphere. The large valve is then 
free to drop to the full opening, allowing free communica- 
tion between the cylinder and the auxiliary clearance 
chamber. The valve will remain open as long as the 
vacuum is below its safe limit. 

When the vacuum returns, atmospheric pressure under 
the valve will lift it as soon as sufficient vacuum is 


FIG. 36. AUXILIARY EXHAUST VALVES USED FOR NON-CON- 
DENSING OPERATION 


obtained. Thus the valve A will close and admit steam 
through D into chamber B which will again hold the valve 
in position for condensing operation. 


NON-CONDENSING OPERATION 


Where Chuse engines are designed for non-condensing 
operation, the same sort of admission valves and operating 
mechanism is used as on condensing engines. The auto- 
matic compression relief valves are replaced by auxiliary 
exhaust valves, located on the side of the cylinder at the 
end of the piston travel. These exhaust valves are operated 
by the same sort of cams and slide mechanism as steam 
valves, except that they are driven by a fixed eccentric 
instead of by the governor. 

Figure 36 shows the manner in which the auxiliary 
exhaust valves are located on the cylinder. Part of the 


61 


cylinder steam passes out through the center exhaust ports 
as soon as these are uncovered by the piston. The cylinder 
is then filled with exhaust steam at atmospheric pressure 
which is allowed to excape through the auxiliary exhaust 
valves until about 7/10 of the return stroke is completed. 

Steam flows from the ends of the cylinder bore through 
the passage A and passing around the open valve, enters 
the central exhaust pipe through the passages B and C. 


HARRISBURG ENGINE USssEs PISTON VALVES 


In the unaflow engines built by the Harrisburg - 
Foundry & Machine Works, central exhaust ports are pro- 
vided but, in place of the customary steam valve for each 
end of the cylinder, a single piston valve is used similar 
to the type used on high-speed engines. Another feature 
of this engine is the use of auxiliary clearance space. 

Figure 37 shows the action in diagrammatic form. In 
position 1, the piston is commencing its stroke, and the 
valve is just opening and admitting steam. Exhaust is 
passing to atmosphere through the central ports and emp- 
tying the auxiliary clearance chamber EGE. In the sec- 
ond position, the steam valve is open, admitting steam 
behind the piston and the exhaust valve is open at the 
opposite end. The central exhaust ports are closed and 
compression is beginning in the cylinder and auxiliary 
chamber EGE. In position 3, the piston is in the position 
of cut-off, the valve having reversed its movement, and the 
admission ports are closed shutting off the supply of steam 
to the head end of the cylinder. Expansion commences 
with the exhaust ports still open at the opposite end and 
compression continues in the auxiliary clearance chamber 
EGE. 

As shown in position 4, the outer edge of the valve 
opens the port at the head end, allowing steam from the 
auxiliary clearance chamber EGE to pass into the cylinder, 
mixing with the expanding steam and expanding with it 
until the central exhaust ports are open to the atmosphere. 
In the mean time the opposite end of the valve has closed 
the exhaust ports and compression occurs in the cylinder 
and cylinder clearance only. 

At position 5, the central exhaust ports are uncovered 
by the piston and the steam is exhausted reducing the pres- 


62 


sure in the cylinder and auxiliary clearance chamber EGH 
to exhaust pressure. At position 6, the stroke is completed 
and the piston is at the end of the cylinder ready for the 
return stroke. In this position the valve is opening to 
admit steam to the crank end the exhaust valve at the 
opposite end is still open and head end exhaust continues. 

For condensing engines, clearance pockets are provided, 
which are placed in communication with the cylinder by 
hand-operated valves, should the engine be required to run 
non-condensing. 


Ae USS as SESE RS Se 


SS | 


Position No. 5 ; Position No. 6 


FIG 37. CYCLE OF OPERATION FOR’ THE HARRISBURG 
set ‘ENGINE 


63 


In Fig. 38 are shown the types of valves which are used 
in this engine. *They are the balanced piston type made 
with adjustable steam-packed rings and operate in remov- 
able cages or bushings. For the smaller sized engines the 
single ported type is used, while the larger engines are 
fitted with the double ported valve. 


SETTING HARRISBURG PISTON VALVES 


While the general method used in setting piston valves 
is apphecable to setting the valves of the Harrisburg una- 
flow, the procedure will be taken up detail. After the 
crank dead center has been located the eccentric rod is . 


4 


! ae (e- 
“i a d 


FiG. oc. TYPE OF PISTON VALVE USED IN HARRISBURG 
ENGINE 


adjusted in length until the valve block to which this eccen- 
tric rod is pinned, moves equal distances from the center 
of the valve block guide when the eccentric is moved to the 
two extremes of its throw. After this has been done, the 
valve is disconnected from the block and drawn out of 
the steam chest. Templets of the valve and the valve 
bushing ports are made as outlined in the method for set- 
ting piston. valves. 

Templets of the valve and the valve bushing ports are 
made and the distance of each port edge from the face of 
the steam chest is measured by the measuring rod. The 
port dimensions, as well as those of the valve, are marked 
off from the point X, as shown in the Fig. 39. 

The valve templet is then shifted until it covers the 
head end and crank end steam ports by equal amounts, so 
that there will be equal laps. The distance from X to the 
valve templet is measured and replacing the valve in the 
steam chest end with the eccentric in mid-position, or the 
valve slide block at the center of its travel, the valve rod 
is adjusted until the end of the valve is the same distance 


64 

from the face of the steam chest as is the valve templet 
when set with equal laps. The governor weight should be 
placed in the normal position for full load conditions. The 
engine should be set on head and crank dead centers, and 
the position of the valve measured and transferred to the 
templet. If the valve has been set properly, the leads 
should be equal. 

After this is done the governor spring should be 
removed and the weight arms shifted to their extreme out- 
ward or no load position. The travel of the valve should 


— 
= 


3 


DA AAIII 


a ; 


WN 


SSS 


\ gee 
TZ. 


FIG. 39. MEASURING VALVE PORTS FOR TEMPLET 


be checked and referred to the templet to determine 
whether the valve uncovers the ports. If the port is uncov- 
ered, it will be necessary to remove the valve, and screw 
the ends together until the amount of lap is sufficient to 
keep the valve closed when the governor is at its outermost 
position. 

It is important that the compression be kept below the 
initial pressure by 5 to 10 lb., which can be checked by 
means of indicator diagrams. If it is desired to increase 
or decrease lead, this can be done by nuts on the valve 
stem where the valve heads are locked. ‘To increase lead 
lengthen the distance between valve heads and, to decrease 
lead, shorten this distance. 


CHAPTER VII 


HAMILTON, KINGSFORD, MURRAY AND 
NORDBERG VALVES 


@ NE point of difference in the Hamilton unaflow engine 
which is built by the Hooven-Owens-Rentschler Co. 
makes it rather distinctive. The steam valves are placed 
horizontal at the bottom of the cylinder as illustrated in 
Fig. 40. These valves are of the double-beat poppet type 
and seat in removable cages. They are driven by an eccen- 
tric operated by a lay shaft running alony the frame, which 
shaft is connected to the crank shaft by double gears and 
a drag crank. ‘The exhaust valves, which are on top the 
cylinder, are also driven by this lay shaft. 

In the steam valve the cam end of the valve stem fits 
into a crosshead X carrying a roller, Y. This roller makes 
contact with the cam, Z, which is clamped on the short 
steam cam shaft, W. This cam shaft is driven by the 
steam eccentric rod, O, by means of a rocker arm clamped 
to the steam cam shaft. Only one steam eccentric is used, 
the two valve cams being fastened to the one steam cam 
shaft. 


SETTING HAMILTON VALVES 


When settinz valves, the first step is to make sure that 
the rollers and cams are in proper contact. lf properly 
adjusted, the back of the cam is exactly vertical, when con- 
tact is made with the roller. 

Adjustment of the eccentric rod is then made, so that 
the distance from the center of the eccentric strap to the 
center of the stub end is 1% in. less than the distance from 
the center of the cam shaft to the center of the governor or 
eccentric shaft. This stub end is now connected to the 
cam shaft lever and the side shaft coupling is disconnected, 
so that the part of the lay shaft carrying the governor and 
eccentric is free from the portion geared to the engine 
shaft. 

After this is done, the governor is turned to bring the 
slide block at right angles to the eccentric rod, which is 


66 


determined by the fact that, when the position is reached, 
it is possible to move the governor in and out without 
moving the cam shaft lever. This is the lead position. 
With this engine is furnished a dial which may be 
clamped to the governor shaft and set to indicate the per- 
cent lead. If this dial is used, it should be set at 2 per 


Ehaust cam 
clamped to shart 
also set screw used.-*%- 


x Adjustable auxiliary 


Pe cecnns ee 


‘eae valve stein 


wnee| 
we 


GER 
AN 


RAwwkee Are Fe 
ji a A Ses ee a 
SSN TUL LA = 


% 
zy 
(> 
sess 
Sam 
SSO . 
Asie 
} pee. 
PLL 


YZ 
~ ri 


Auxiliary exhaust 
‘ eccentric 
i) 


Ef, 


SS ZEZZIZZLLIS /Y eccontric eccentric 
\ 6 ea SF Ni SN Sn S Governor shaft 
Annannnn SSS CEES Z vs ofa. 2 me a 
{ Zea WSS eth < 7 yA ve || mM 
: ES a : AD H 
=, ial 


FIG. 40. HORIZONTAL VALVE USED WITH HAMILTON 
ENGINE 


cent lead. If the dial is not available, marks can be made 
on the shaft and bearing. 

Revolve the shaft one-half turn and the other cam 
should just begin to push its roller at 2 per cent lead. This 
should be the condition when the governor springs are 
removed and the weight blocked half way out. When the 
governor weights are at the extreme outer position, the 
valve should not be opened at all by the cam. When the 
weights are entirely in, the maximum opening and cut-off 
are obtained. 


67 


In this engine, the cut-off and openings are equalized 
by changing the length of the eccentric rods and the lead 
is changed by shifting the governor shaft coupling so that 
the eccentric is advanced with reference to the crank pin. 

When the engine is tested at the factory, a mark is 
made on the coupling opposite the pointer mark on the 
bearing and stamped “crank-end center.” The shaft is 
then turned a slight amount until the dial shows crank- 
end lead and another mark is placed on the coupling and 
lettered “crank-end lead.” These two marks make it pos- 
sible to check up the valve setting at any time. 

Where the engine is to be used for condensing opera- 
tion, it is fitted with auxiliary exhaust valves placed at the 
top of the cylinder. These valves are of the double beat 
type and are controlled by cams fitted to a short cam shaft 
along the cylinder top, which is driven by a single exhaust 
eccentric from the main layshaft. 


RELIEF VALVES FOR CONDENSING SERVICE 


Where the engines are used for condensing service, 
relief valves are placed at each side of the cylinder and 
communicate with a clearance belt or passage around the 
cylinder. If it is desired to run non-condensing, these 
valves are opened by hand and add the auxiliary clearance 
volume to the normal cylinder clearance. 

When setting the exhaust valve, the exhaust eccentric 
rod should be disconnected from the camshaft rocker, and 
the exhaust cam should be adjusted for quiet operation by 
screwing down the cap nut on the end of the exhaust valve 
stem, until the valve is too short. The nut is then grad- 
ually screwed up until the noise disappears, although a 
precaution should be taken that the stem is not left too 
long. The eccentric rod is then reconnected and the cams 
are set by shifting the exhaust eccentric to its position of 
minimum travel. 

Next the governor shaft is rotated until the exhaust 
cam shaft is at one extreme of its travel, and the proper 
cam is set to bring its flat side level or horizontal. After 
this it is necessary to rotate the governor shaft about one- 
half a revolution or until the other extreme of the cam 
shaft oscillation is reached. Then the second cam is 
clamped with its flat side level. The check on whether the 


68 


proper setting has been made, is to turn the governor shaft 
through an entire revolution. If the exhaust valve does 
not open, the setting has been properly carried out. 

When the eccentric is shifted to any position other than 
that of least travel, both valves should have equal lifts. 
This exhaust valve gear is so designed that the valves open 
at about 6 per cent of the stroke past dead center and may 
be adjusted by the hand wheel to close at any point in the 
exhaust stroke up to 95 per cent. The lead is always 
constant. 


=== 
{ TN 
\ 


BN 8 
a 


[TI 
SHS oe 
Lie, 


Ws 


Vi 
NZ 


SSSSSAG 


SMA 


FIG. 41. VALVE GEAR OF KINGSFORD ENGINE 


Set the engine crankpin on the crank-end dead center, 
rotate the governor shaft until the index of the bearing 
shaft coincides with the line marked “crank-end center” on 
the coupling and clamp the coupling. This completes the 
valve setting. 


KINGSFORD UNAFLOW ENGINE 


Figure 41 shows a cross-section through the valve gear 
of the unaflow engine built by the Kingsford Foundry & 
Machine Works. ‘This view shows the crank on the head- 
end center with the active part of the head-end steam cam 
and crank end exhaust cam about to engage in the open- 
ing of their respective valves. Similar conditions, apply 


69 


with the crank on the opposite or crank-end center. The 
location of the keyways in the cam shaft (steam and 
exhaust) and lay shaft for the eccentric and governor are 
determined from the valve diagram. 

To set the cams so as to give correct timing of valve 
opening is a simple matter, and the general procedure is 
as follows: 

Place the engine in any position off center so that the 
inactive part of the cam face engages the roller (steam or 
exhaust). Give the steam valve tappet about 0.006 in. 
clearance and the same clearance for the exhaust, measured 
by slipping a feeler gage under roller B and making 
adjustment at C. 

The next step is to turn the engine over and place the 
crank on either center. To simplify matters, we will place 
the crank on the head-end center and follow the points of 
adjustment from the drawing which, as previously men- 
tioned, shows the position of cams with crank on head end. 

For good running conditions 0.003 in. clearance be- 
tween cam face and roller is sufficient. Try a 0.003 feeler 
between steam tappets at A and, if this space is greater, 
slack nut on eccentric pin D, and with a small wrench on 
the square head turn the cam clock-wise until the 0.003 
feeler pinches at A. This completes the setting of the 
steam cam. Give the exhaust cam the same clearance and 
proceed in a like manner with crank on opposite end. 

The final valve adjustments should of course be made 
with an indicator. 

For control of the steam valves, a centrifugal inertia 
governor is used, mounted on the lay shaft and equipped 
with two eccentrics, primary and secondary, which com- 
bination is dead beat. 

The primary eccentric is keyed to the lay shaft and the 
secondary is connected to the governor weights by means 
of links. This combination of double eccentrics is also 
used for the exhaust valve drive with the secondary adjust- 
able to vary the compression. 


Murray UNAFLOW ENGINES 
As will be noted from Fig. 42, the unaflow engine built 
by the Murray Iron Works Co. utilizes the poppet type of 
valve. These valves are of the double-beat type with the 


70 


lower valve seat attached on the valve body, while the 
upper valve seat is a light flexible steel disk held to the 
valve body by set screws. It is stated that the use of one 
flexible seat reduces the possibility of steam leakage, which 
exists when the entire valve is made in one piece. The 
upper valve disk rests on a seat turned on the head casting, 
while the lower valve edge rests on a seat that is a separate 
casting held to the cylinder head by a cap screw. 
Referring to Fig. 42 the valve rod marked X is driven 
by the governor eccentric and to this rod are fastened two 


8 a 
ap EADS Yy. Wis. A = 
ia ow) ) | --— ta INT] 
@ — a lags 


FIG. 42. VALVE ARRANGEMENT OF MURRAY UNAFLOW 


steel blocks A, one to slide in each valve bonnet. Hach 
block carries a roller which makes contact with a cam block 
B, placed on a crosshead fastened to the valve stem. ‘The 
roller C, due to the reciprocating motion of the valve rod, 
makes contact with the cam B raising the valve stem and 
so admitting steam to the cylinder. 

When the valves are set, the engine is turned over until 
the roller C is under the flat surface of the cam D. The 
valve stem is then turned until the clearance between the 
cam and roller is 0.002 in. which insures that the valve 
will be closed when its roller is under the flat surface of 
the cam. 


14 
ADJUSTING MuRRAY VALVES FOR LEAD 


Lead is adjusted by uncoupling the valve rod X and 
setting the eccentric rod so that the rocker arm travels 
equal distances each side of its vertical position. This 
reach rod, X, should then be adjusted to a length such that, 
when the engine is on crank dead center, the roller just 
touches the cam of the crank-end valve. 

Next the rod Z is adjusted by the turn buckle, Y, so 
as to cause the head-end valve roller to touch its cam, when 
the crank is at head-end dead center. 


This engine also uses auxiliary exhaust valves, which 
are of the solid piston type and are moved by a fixed eccen- 
tric, through a linkage as shown. In order to set the auxil- 
iary exhaust valves an opening is provided into which a 
relief valve is screwed so that the engineer can see the 
auxiliary port slot through the exhaust valve cage. The 
valve is set so that the top edge is in line with the lower 
edge of the slot when wide open; that is, the valve opens 
wide without any over travel. When closed, the lap is prac- 
tically one and one-half times the length of the slots. This 
is necessary in order to keep the valve closed during half 
the engine’s revolution. After setting the two auxiliary 
valves so that their travels and positions are as near alike 
as possible, by changing the valve stem and reach rod 
length, the exhaust eccentric should be shifted to give a 
small amount of lead with the engine on dead center. If 
the valves do not show the same lead, correction may be 
made by adjusting the rocker arm to get equal travel each 
way from its vertical position and by changing the length 
of the reach rod. 

As in other types of engines, it is recommended that 
final adjustment of all valves be made, after the engine 
has been run awhile, by taking indicator diagrams. Auxil- 
lary exhaust valves must be set to give correct compres- 
sion for the existing back pressure and, when operating 
condensing, the auxiliary valves are uncoupled or left off 
entirely. 

In this engine the cylinder body is not steam jacketed 
but is covered with several inches of insulating material. 
Steam is admitted to each cylinder head through a cast- 
iron pipe connection and the cylinder heads are steam 


ANIOND MOTAIVNA 


Vv Ao 


NOILVTVIVISNI 


TVOICAL 


"OE ‘DLT 


73 


jacketed, the faces forming the steam chest for the engine. 
In this way condensation is reduced to a minimum. 


NORDBERG VALVES DRIVEN BY LAYSHAFT 


in Fig. 44 is shown the valve arrangement of the una- 
flow engines built by the Nordberg Manufacturing Co. 
As shown in this sectional view, both the steam and exhaust 
valves are driven by means of a lavshaft upon which the 


oe 


a4 NY 

“ap i 

¢ somo ot \ 
TOCA A a 
WA 


NSS Sas 
& | 
SULT Ts 
eeeoue 


A 
Ge 
w 
8 & 
y 
N 
N 
N 
N 
NY 
soy 


3 
4 
% 
edt 


FIG. 44. NORDBERG VALVES ARE PLACED IN CAGES 


eccentrics are placed and which is driven by the crank 
shaft through bevel gears. A centrifugal type of governor, 
connected to the steam eccentric by a sleeve, controls the 
engine speed by altering the eccentric travel and the lift 
of the steam valve. | 

Valve action is obtained by the use of cams. Both the 
steam and exhaust valves are arranged in cages which set 
into the cylinder casting. 

Referring to Fig. 44 both steam and exhaust valves are 
operated by a cam lever which is actuated by a cam and 
rollers. When eccentric rod H moves upward, the cam X 
is rotated inwardly. This cam makes contact with the 


74 


opening roller and at the same time the back part of the 
cam X which is depressed comes under the closing roller 
Y. ‘The steam reach rod H, as it moves upward, causes 
the cam to push the roller D upward and the cam lever 
A moves about the fulcrum pin W. This causes the valve 
to lift off of its seat and admit steam to the cylinder. As 
the eccentric continues on around its circle, the operation 
is reversed, and since the cam has a steep slope at the 
points of contact with the roller, opening and closing of 
the valves are rapid. 

When the valve seats, further travel of the cam causes 
the valve stem to compress the valve spring, insuring posi- 
tive valve closing and also exerting downward pressure on 
the valve when it is seated. ‘These cams carry two marks, 
one showing the exact point of closure of the valve and 
the other showing the point where the connecting spring 
first comes under full compression. 


CaM AND ROLLER CLEARANCE 


When setting the valve, the fulerum D of the cam is 
turned eccentric so that the cam can be adjusted with the 
proper amount of clearance between the cam and roller. 
As in other valve settings which have been described, this 
clearance is about 0.003 in. In adjusting the length of the 
valve stem, care must be taken that the compression of the 
spring does not become excessive. In making this adjust- 
ment, the engine should be turned to a point where the 
valve is closed and the stem then adjusted so that the coils 
of the spring are not forced together so much that contact 
is made between the coils. 

The actual valve setting is carried out along lines 
which have been described. First the engine is turned to 
dead center, the governor weights are blocked in the outer- 
most position and the eccentric rod is adjusted so that the 
valve is not lifted but remains seated. In this case the 
cam should clear the cam lever roller. 


PROVISION FOR NON-CONDENSING OPERATION 


In order to take care of either condensing or non-con- 
densing operation, the exhaust cam is made with excep- 
tionally long contact faces so that, when operating con- 
densing, the valve can be kept closed and the rollers kept 


75 


in contact with the cam while the eccentric is giving the 
full stroke to the cam. The opening point of the exhaust 
valve is not so important but the point of closing must be 
set according to the operating conditions desired. This 
point of closing of the exhaust valve is changed by changing 
the effective length of the exhaust eccentric rod. This is 
done by introducing a combination lever M, which is car- 
ried by a rocker, the rocker arms for both the exhaust valves 
being adjusted by means of one hand lever. This adjust- 
ment can be made when the engine is in operation. By 
placing the hand lever in different positions, the point of 
closing of the exhaust valve can be changed as desired to 
fit any operating conditions. 


CHAPTER VIII 


RIDGEWAY, SKINNER AND WORTHINGTON 
VALVE SETTING 


DMISSION valves of the unaflow engines built by 
the Ridgway Dynamo & Engine Co. are of the double- 

beat poppet type and are placed in the cylinder heads. In 
order to compensate for slight variation in vertical dis- 
tance between the upper and lower seats, such as might be 
caused by expansion due to temperature changes, the upper 
lip of the valve is made thin enough to have slight flexi- 
bihty. The steam pressure above then aids in forcing the 
valve tightly on both seats and steam leakage is prevented 


FIG. 45. ADMISSION VALVE OF THE BIDGEWAY ENGINE 


77 


Motion from the governor eccentric is transmitted 
through an operating rod on the top of the bed, to the 
ram passing through the upper part of the valve bonnet. 
This ram carries a hardened and ground steel roller which, 
coming into contact with the cam above it, raises the stcel 
sleeve to which the valve rod is connected, and in turn 
lifts the valve. Figure 45 shows the construction of the 
valve and lifting mechanism and the means provided for 
adjusting various parts. The valve stem passes through a 


Lee oy 
i 4 
I 4 4 Uy 
a ao YY 
=f Mii 
7 Go by YY Ve 
A 4 hye yy 
yw 4 wy OY! 
Uh, Mi =, Wy yg Iie 


OSA os 
, y fi o x 


FIG. 46. RELIEF VALVE USED IN CONDENSING SERVICE 


long guide or stuffing box. A series of grooves is turned 
on the stem and these grooves, becoming filled with water, 
form an effectual seal against steam leakage. 


ARRANGEMENT FOR CONDENSING SERVICE 


Engines built for condensing service have an auxiliary 
clearance space in each head. The connection to this space 
is through a combination drain, relief and clearance valve, 
a section of which is shown in Fig. 46. The large hand 
wheel opens the connection to the clearance space and the 
small wheel opens the drain. 

Between these valves is a spring-loaded relief valve 
which can be adjusted by an outside nut. When the engine 
is operating condensing, the clearance valve is closed. 
Should the vacuum fail, the relief valve will open to pre- 
vent excessive pressure, until such time as the clearance 


78 


valve can be opened by hand, under which condition ample 
clearance space is provided for non-condensing operation 
and, at the same time, the relief and drain portions of the 
valve function as before. Engines designed for non-con- 
densing service only, have pistons with concave heads to 
provide the volumetric clearance necessary to prevent 
excessive compression. 


ARRANGEMENT OF RIDGEWAY VALVES 


In Fig. 47 is shown a sectional view of the cylinder 
which gives an idea of the arrangement of the valves. 


bo Hh 


; af NZ2 
a : \ 
Van <a | lf 
Li Ns : Cae E> MI = || 1 
- ) KA or AG 


Ee 
Sal ie 


Lida 


. SI yb isan 

He SS |} ae 
ae, wn Eye 

eS im: Vail ase 


SOW EE 


y 
N 
RY 
AY 
Ny 
N 
N 
N 
N 
N 
N 
N 
N 
Ny 


FIG. 47. VALVE ARRANGEMENT IN THE RIDGEWAY ENGINE 


Referring to this figure and the previous illustration show- 
ing the section of the steam admission valve, the operation 
of the valves is as follows: The reach rod C is operated 
by the governor-controlled eccentric, the motion being 
transmitted through an eccentric rod and rocker arm, 
through the cam rod B. The roller C which is a part of 
the cam rod B comes in contact with the cam D and 
operates the valve. 

Setting the steam valve is a procedure quite similar to 
that followed in similar types of valvespreviously described 
but will be reviewed briefly. The reach rod D is first dis- 


_ 


79 


connected, and the length of the valve stem is adjusted to 
give a clearance between the cam D and the roller C of 
0.002 in. when the roller is under the thin part of the cam. 
This clearance must be kept small as, if it is made much 
greater, there will be a pound when the roller strikes the 
cam while the engine is running. 


ReacH Rop ADJUSTMENT 


After reconnecting the reach rod to the cam rod B, the 
engine is turned over until it is within 1 per cent of its 
stroke of reaching crank dead center. ‘This is the lead 
point and the reach rod C should be so adjusted that the 
valve will start to lift at this point. In a similar way the 


FIG. 48. EXPANSION RINGS PREVENT LEAKAGE IN SKINNER 
VALVES 


engine is turned over in its running direction until within 
1 per cent of the stroke, of head dead center. In that posi- 
tion the head-end steam valve is set to cause the valve to 
start to open. This adjustment is made by altering the 
length of the tie rod connecting the two cam rods. This 
tie rod has right and left hand threaded ends so that it is 
easily possible to change the distance between the cam 
rods. 


As in other engines, it is recommended that the engine 
be run for a time and indicator diagrams taken. If the 
lead is not correct, the proper change in timing should be 
made. It is also advisable to check the cam clearance when 
the engine is hot, as the engine will take steam for the 
full stroke unless there is some clearance between this cam 
and its roller. 


80 


SKINNER UNAFLOW ENGINES 


Unaflow engines built by the Skinner Engine Co. 
utilize a steam valve of the double-beat poppet design. 
This valve also is of a design which eliminates leakage due 
to unequal expansion of the valve and cylinder head. 
Figure 48 shows how the top portion of the valve is sep- 
arated from the valve body and is held down by spring 
tension. Expansion rings shown at A prevent steam leak- 
age between the two parts of the valve as any inequality of 


¥. | 4 2 


r fe. 


FIG. 49. VALVE MECHANISM OF THE SKINNER ENGINE 


expansion of the valve is compensated by a slight displace- 
ment of the upper part of the valve body. 

Figure 49 shows how these valves are set in the cylinder 
and also the actuating mechanism which is used. In this 
arrangement the steam valves are operated by a bell crank 
marked X. This crank carries a roller which makes con- 
tact with the cam Z which is a part of the rocker W. 
Movement of the rocker is obtained by the movement of the 
reach rod, O, from an eccentric which is controlled by the 
governor. 

PROCEDURE IN SETTING VALVES 

Valves of this type are set by blocking the governor 

weight in its outermost position as this is the over-speed 


-~ 


81 


position of the governor. When the governor is in this posi- 
tion, the engine is turned in the running direction and the 
reach rod and cam rocker W are adjusted until the cam 
just fails to open the valve. This prevents the engine from 
taking steam when the governor is in the over-speed 
position. 

Next, the steam valve is lifted by the end of the rocker 
X touching the set screw Y. When the engine is turned 
beyond the cut-off position, there must be a clearance 
between the end of the rocker and set screw, so that the 


=| 
al 
=! 
Al 
ul 


LILLPLL A 


i fe 
bi i 


7777 i 


FIG. 50. AUXILIARY EXHAUST VALVES OF SKINNER ENGINE 


valve will be held open. Clearance at this point should be 
about 0.003 in. When the set screw has been adjusted to 
this clearance the engine is turned to crank center. Then 
the governor is blocked in its usual running position and 
the valve reach rod is adjusted so that the rocker X just 
makes contact with the set screw Y when the crank is on 
dead center. 

After this is done, the engine is turned to the head-end 
dead center and the reach rod is adjusted so that the rocker 
X just strikes the set screw Y on the head-end valve. The 
valves are now correctly set, although as a precaution it is 
well to block the governor again in the extreme outer 


82 


position and check the clearance between the cam and the 
rocker. 


AUXILIARY VALVES 


In Fig. 50 is a sectional view of the auxiliary exhaust 
valves which are used with the Skinner engine. In setting 
these valves, it is necessary that the eccentric rod be of 
such length that the rocker arm to which it is attached 
will move the same distance from its vertical position, 
when the eccentric is moved to its two extreme positions. 
The next step is to determine the lift of the valves. This 
is done by removing the covers from the sides of the 
exhaust cam boxes after draining out the oil. Chalk is 
then rubbed on the sides of the cam shifter A, which is 
under the exhaust valve stems B, and a vertical line scribed © 
on it, in line with the valve stem. With the calipers rest- 
ing on the inside of the bottom of the exhaust-cam box, . 
scribe a line on the side of the cam shifter when the exhaust 
valve D is down on its seat in a closed position. After 
this is done, turn the engine and scribe a line on the side 
of the shifter when the valve is in its topmost position. 
The difference between these lines represents the lift of the 
valve which should be as follows: 


Engine Stroke Lift of Valve 
15 no A ee ee 5@ in. 
16 D's soy hae een fee ee 5@ In. 
AB IN nS is eC peo cnt cee ee 34 in. 
PAU rea ert ge AR 34 in. 
Pak Cae Re E Mee eee et 43 in 
BA. | AD pou schon wit ns east pe a ee 43 in 
PLS MM ee SO aR ee 42 in 
BO. 1s si1) oe spcemlaleus ahg§s stn tn Dee eae en Lowe 
BO) ADL 2 io oie :otnisn: nl Tun do SGA ib dee et yes | 


It is possible to regulate the valve lift by movement of 
the exhaust reach rod, which has right and left hand 
threads. In making the adjustment the crank-end valve 
should be adjusted before the head-end valve. When the 
exhaust valves are closed, the end of the stem should clear 
the shifter by the thickness of an indicator card. In check- 
ing the wide open position of the valve, it is well to make 
sure that it is not striking anywhere, at its extreme normal 
lift, by opening it a little farther with a lever. 


83 


SHIFTING THE ECCENTRIC 


When the rods have been adjusted for proper lift, the 
time of opening and closing may be regulated by adjusting 
the eccentric on the engine shaft. It should be shifted 
so that the crank-end valve will close just before the pis- 
ton reaches the crank end of its stroke. When it has been 
set in this position, the crank-end valve will open imme- 
diately before the piston reaches the head end of its stroke. 

In a similar way the head-end exhaust valve should 
be checked to close just before the crank is on the near 
dead center and to open before the crank is on the far 
center. It will be found that the eccentric is marked on 
the side toward the engine bed corresponding to a mark 
on the shaft which shows the setting made at the time 
the engine was under test at the manufacturer’s shop. 

In large engines of the Skinner type, a slight change 
is made in the type of valve gear which is used. Although 
the valve itself is identical with those shown, the cam 
rockers are mounted on a shaft running along the cylinder 
which is driven by a linkage from the governor eccentric. 
The face of the valve cam is also made wider so that the 
valve-lifting lever and roller slide along the face when the 
cylinder expands on warming up. The method of setting 
the steam valve is the same, however, as for the smaller 
engines, 


WorTHINGTON UNAFLOW COMPRESSOR 


Valves in the unaflow engine-compressor which is built 
by the Worthington Pump & Machinery Corp. are set 
horizontally in the bottom of the cylinder head as shown 
in Fig. 51. These valves are of the double-beat poppet 
type. The cast-iron valve body M slides on an extension 
O of the valve bonnet. The valve rests on the cylinder 
head casting and carries seat R which is a light steel ring 
shrunk onto the valve body. This ring is somewhat 
flexible and it takes care of the difference in expansion of 
the cylinder head casting and valve body. 

It will be noted that the valve stem has a spiral groove 
in in it. Oil passes along the groove to the end of the | 
valve and so lubricates the valve stem and sleeve. 

Operation of this valve is due to the rotation of a lay 
shaft geared to the crank shaft. Two cams, one for each 


84 


cylinder end are fitted to a cam shaft, which is engaged 
by the lay shaft by means of a feather key. One of these 
cams is shown in Fig. 52. The rotation of the lay shaft 
causes the nose of the cam to strike the cam lever roller, 
which is connected by a link X to the valve lever Y. The 
motion of the cam is thus transmitted to the valve which 
is lifted off the seat and steam is admitted to the cylinder. 
At Z is the valve tappet which is engaged by the cam 
lever Y. 

It will be noted that the governor fits directly over the 
governor box and is driven by means of double gears from 


Ji Steam a 


der head, / jacket ee 


ee a 


“Relief valve 
connectioir 


FIG. 51. HORIZONTAL VALVES ARE USED WITH WORTITING- 
TON ENGINE 


the lay shaft. As the engine drives a compressor, there 
is also a pressure governor mounted on the base plate 
between the cylinder housings. This governor is of the 
diaphragm type and the discharge air pressure operates 
a small pilot valve which in turn admits liquid pressure to 
the operating piston. Movement of the piston is trans- 
mitted through an adjustable rod to a push pin which, 
pressing against the bell crank, moves the cam shaft. 
When the compressor is operating below the discharge 
pressure for which the governor of the engine is set, the 
engine will run at maximum speed for which the speed 
governor is set. As soon as the air pressure reaches the 
desired maximum, a bell crank shortens the cut-off and 
slows down the machine. | 

In engines of the duplex type, that is with two parallel 
cylinders, two sets of cam rockers are provided for each 


85 


cam, as shown in Fig. 52. This shows how the valve rod 
connection is made to the opposite cylinder. The main 
engine cranks are set at 90 deg. and the rollers in contact 
with the head-end cam are spaced at 90 deg. as are also 
the rollers of the crank-end cam. The cams are keyed to 
the shaft at 180 deg. 


FIG. 52. VALVE OPERATING MECHANISM 


Since the setting of the four steam valves is fixed in 
this way, the only valve setting necessary is the exact posi- 
tion of the bevel gear on the main engine shaft, as the 
position of this gear determines the lead or admission. 
The lead should be such that the steam valve is 35 in. 
open when the engine is on each dead center. 

It is advisable to determine the exact position of this 
gear by the use of an indicator. The lobe of the cam is 
tapered so that, with the speed governor in its lowest pos- 


86 


sible position, the cut-off in each cylinder is approximately 
50 per cent, while with the governor in its highest possible 
position, the cut-off is zero. As the admission side of the 
cam lobe is a straight line parallel to the axis of the cam- 
shaft, the same admission point is maintained regardless 
of cut-off. The back or cut-off part of the cam is tapered 
so as to give the range of cut-off as stated. 

Clearance of the valve tappets should be about 0.002 
to 0.003 in. when the engine is warmed up. This adjust- 
ment is made by changing the length of the valve rod X 
and the amount of clearance can be determined by insert- 
ing a thickness gage between the tappets. This clearance 
should be checked when the roller is on the base circle of 
the cam and not on any part of the lobe. If the clearance 
is not correct the valve will be noisy, will have insufficient 
lift or will remain slightly open at times resulting in a 
loss of economy. 

Although no auxiliary exhaust valves are used with 
this engine, it is built for non-condensing operation by 
the use of clearance chambers which are attached to each 
of the heads. These clearance chambers are opened by 
means of hand-operated valves which throw them into 
communication with the cylinder. When the engine is 
built primarily for non-condensing service, the required 
clearance volume is secured by making the face of the 
piston concave. 


CHAPTER IX 
GOVERNING THE ENGINE 


OWER developed by an engine may be altered by 

changing either the initial pressure or the point at 
which the engine cuts off. In the former case the area at 
the top of the indicator diagram, as shown in Fig. 53, is 
reduced, while in the latter method the expansion area is 
reduced. - 


THROTTLING OR VARIABLE CuT-oFF USED 


Governors operate on one of these two principles, 
although the throttling type is uneconomical since the 
steam is developed at high pressure and used at a lower 


oe . |. 


Throttli 
(A) Throttling (B) Variable Cut off 


FIG. 53. CHANGES IN CARDS CAUSED BY TWO METHODS OF 
GOVERNING 


pressure, thus cutting down the possible efficiency of the 
cycle. For this reason the use of governors for larger 
engines has been mostly confined to the variable cut-off 
- type. 

For varying the cut-off two methods are used; that 
of detaching the valve from the eccentric and closing it 
by a spring or dash pot and that of shifting the eccentric 
so as to alter the lead or travel or both. In the first 
method, the governor controls the point at which the valve 
is released from the eccentric and in the second method 
the eccentric is either turned around the shaft or is swung 
across the shaft on a pivot pin. 

As the detaching governor acts only on the cut-off, it 
alters no other event in the valve operation. While this 
has certain advantages, the type of mechanism used limits 


88 


it to low and medium-speed engines. If the eccentric 
operating the main valve is turned about the shaft, all of 
the events of the stroke are changed. It is desirable that 
the exhaust and compression be altered but little, hence 
this type of governing has to be designed with that point 
in view. It is well adapted to control riding cut-off valves 
through a separate eccentric, the main eccentric being 
fixed. 

It is possible to pivot the swinging eccentric so that 
it will increase the travel of the valve and thereby lengthen 
the cut-off and, at the same time, it may increase or 
decrease the lead at the will of the designer. As a matter 
of fact it is desirable to have the lead decreased as the cut- 
off is shortened, in order to avoid over speeding the engine 
at no load. Increasing the travel gives earlier admission, 
later cut-off, earlier release and later compression, Lead 
may be altered to bring all the events a little earlier or a 
little later, the former being generally used. Decreasing 
travel results in an opposite effect on each event of the 
stroke. 


Two TyprEs oF GOVERNORS 


There are two main types of governors in use, known 
as the fly-ball and shaft governor. In most Corliss engines 
the flyball has the centrifugal force of the balls working 
against gravity, but for higher speeds or more sensitive 
regulation or for other than vertical positions the spring 
is substituted. 

Although the details of shaft governors vary widely, 
they may be classed as two main types; those which use 
centrifugal force only and those in which this effect 
is combined with inertia. As a rule the centrifugal gover- 
nors are used where the eccentric is revolved around the 
shaft, controlling a riding cut-off valve. 

For controlling the valve of a single-valve engine, power 
is required which means a heavy governor weight and it 
has been found best to take advantage of the inertia of 
this weight to increase the quickness of action. 

In any form of shaft governor, changing the spring 
attachment changes the sensitiveness and changing the 
weight adjustment changes the speed. In the centrifugal 
form, increasing the spring tension and the weights will 


89 


increase sensitiveness or attachment of spring or weights 
may be changed so as to give them greater leverage about 
the pin, which has the same effect as changing the tension | 
or weight. 


ACTION OF FLYBALL GOVERNOR 


In Fig. 54 is shown a flyball governor of the type used 
on Corliss engines. This governor has an automatic safety 


Sty 
SSS 


NARA WAARARAARAN RRR 


4 


g 


« 
} m—as| FN 7 
eS yay ANZ 
Vee . 
ze | 
Gy 


GUM Wits Uline 
4 


FIG, 54. ONE TYPE OF FLYBALL GOVERNOR USED WITH 
CORLISS ENGINES 


stop and when the engine is at rest the lever 4 rests on 
the automatic rest 5. This automatic rest is held in place 
by. the rod A and the arm 3 which is connected to the 
idler pulley, 2, resting on the governor belt. 

Should the governor belt break, the idler pulley will 
drop down pulling the automatic rest 5 from under lever 
4 and allowing the lever to drop far enough to bring the 


90 


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safety block on the knock-off lever of the Corliss valve 
gear under the tail plate on the grab hook so that the hook 
plates clears the catch block and the steam valve will not 
open. By this arrangement the engine is ready to start 
and the safety device is always ready for action without 
any attention from the operator. The running speed of 
the governor is 125 r. p. m. By moving the adjusting 
weight 1 in or out, the speed of the engine may be increased 
or decreased several revolutions. 


Section Through 
a wricLeyer 


cert, 


FIG. 55. ROBB-ARMSTRONG-SWEET TYPE OF SHAFT 
GOVERNOR 


in table III are shown some of the results which may 
be expected in making changes in the adjustment of fly- 
ball governors. 

Several types of shaft governors are in use which 
operate on the same principle but differ in mechanical 
details. In Fig. 55 is shown a Robb-Armstrong-Sweet type 
of shaft governor. The eccentric lever for this governor is 
of the double bearing type with a bearing on either side of 
the wheel arm to prevent the overhanging weight of the 
lever from wearing the pins and bushing out of alinement. 

It is possible to increase the speed of the engine by 
increasing the tension on the main governor spring, and 
to decrease the speed by decreasing the tension. If it is 
found that the governor is too sensitive to variation of 


92 


loads, this can be corrected by moving the link in the 
eccentric lever one hole further from the shaft and, if it 
should be found that the governor is too sluggish in action 
or not sensitive to variation of load, allowing a variation 
of speed in the engine, the link in the eccentric lever, may 
then be moved one hole nearer the eccentric shaft. 

An important factor in satisfactory operation of the 
governor is the position of the fulcrum on the main goy- 
ernor spring. If the governor should be unsteady or have 
a tendency to hunt or race, this may be corrected by swing- 
ing the point of the fulcrum further towards the spring 
weight and again locking it in position. 

Shaft governors, employ, for their operation, forces of 
two kinds, first centrifugal force and second inertia. In 
this respect they differ from flyball governors which em- 
ploy centrifugal force, only. 


Most SHAFT GOVERNORS USE INERTIA 


While it is possible to design shaft governors which use 
only centrifugal force to control the speed of the engine, 
it has been found that the governor weight must be made 
so. heavy that the governor is correspondingly slow or slug- 
gish in its action. It is for this reason that nearly all 
shaft governors are so designed that the inertia of the 
weight will assist the governor in changing position. 

In governors of this type, advantage is taken of the 
tendency of a weight to keep on moving at the same speed 
when the speed of the flywheel changes. If the engine is 
running at a constant speed, the fly wheel and governor 
weights will be turning at the same rate. If a load is 
suddenly thrown on the engine, the flywheel speed slackens 
but the inertia of the governor weights causes them to 
move forward at the same rate as before. This movement 
is utilized by some mechanical means depending on the 
particular design of the governor. 


CLASSIFICATION OF SHAFT GOVERNORS 


The shaft governor may be classified with respect to 
the arrangement of weights employed, as follows: 1. Bal- 
anced governors with two weights and their fly wheels in 
continual balance. 2. Balanced governors with a single 
weight and their fly wheels not in continual balance. 3. 


— 


93 


Governors with a single arm which carries inertia weight, 
centrifugal weight and eccentric; the governor and its 
wheel being nearly balanced in all positions. 4. Governors 
having two arms or an arm and a weight, the governor and 
its wheel being nearly balanced in all positions. 

Governors of all of the above classes can be so operated 
that the regulation can be either assisted or retarded by 


ATRAVERSE BLOCK 


tH 


——| 


FIG. 56. HARRISBURG BALANCED TYPE SHAFT GOVERNOR 


inertia and can be connected to a rotating or a swinging 
eccentric as desired. In most of the governors used, how- 
ever, inertia assists the regulation. 

In Fig. 56 is shown another type of shaft governor, of 
the centrally balanced centrifugal inertia type. In this 
type the weight arms are constructed with differential 
weight pockets to allow a considerable range of speed 
adjustment without altering the tension of the springs. 
If an increase of speed is desired, remove weights of equal 


94 


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95 


thickness from the two weight pockets of the lever and, 
to obtain a decrease of speed, add weights of equal thick- 
ness. If an increased number of revolutions causes the 
governor to race, move the attachment block, in the slot to 
which the outer end of the spring is attached, farther from 
the small end of the weight lever. If this does not entirely 
correct the sensitive condition, the plug is screwed into the 
spring until the racing ceases. 

If the decrease of speed so obtained renders the gov- 
ernor too sluggish in action, move the attachment or 
traverse block in the slot in the opposite direction. If this 
does not improve the regulation and the speed is lower 
than desired, weights of equal thickness are added increas- 
ing the spring tension until the proper speed is obtained. 

Table IV shows the effect on shaft governors due to 
changing the spring tension or making a change in the 
governor weights. 


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